Support the latest pkg:csslib on the 0.13 version path (#97)

If folks have not upgraded to the latest pkg:html, they should still
be able to get the latest pkg:csslib

(This is particularly important since there is a pkg:analyzer dependency
here that moves slowly.)
diff --git a/.travis.yml b/.travis.yml
index 714aa86..353f809 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,8 @@
 language: dart
 dart:
+  - 2.0.0
   - dev
+
 dart_task:
   - test: -p vm
   - test: -p chrome,firefox
@@ -13,7 +15,7 @@
 
 # Only building master means that we don't run two builds for each pull request.
 branches:
-  only: [master]
+  only: [master, v0_13]
 
 cache:
  directories:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 14eb41c..350ac50 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.13.4+2
+
+- Support `package:css` `>=0.13.2 <0.16.0`.
+
 ## 0.13.4+1
 
 * Fixes to readme and pubspec.
diff --git a/lib/src/constants.dart b/lib/src/constants.dart
index fc0c6a1..34addfc 100644
--- a/lib/src/constants.dart
+++ b/lib/src/constants.dart
@@ -29,10 +29,10 @@
       "Entity used with illegal number (windows-1252 reference).",
   "cant-convert-numeric-entity":
       "Numeric entity couldn't be converted to character "
-      "(codepoint U+%(charAsInt)08x).",
+          "(codepoint U+%(charAsInt)08x).",
   "illegal-codepoint-for-numeric-entity":
       "Numeric entity represents an illegal codepoint: "
-      "U+%(charAsInt)08x.",
+          "U+%(charAsInt)08x.",
   "numeric-entity-without-semicolon": "Numeric entity didn't end with ';'.",
   "expected-numeric-entity-but-got-eof":
       "Numeric entity expected. Got end of file instead.",
@@ -46,7 +46,7 @@
       "Expected tag name. Got '>' instead.",
   "expected-tag-name-but-got-question-mark":
       "Expected tag name. Got '?' instead. (HTML doesn't "
-      "support processing instructions.)",
+          "support processing instructions.)",
   "expected-tag-name": "Expected tag name. Got something else instead",
   "expected-closing-tag-but-got-right-bracket":
       "Expected closing tag. Got '>' instead. Ignoring '</>'.",
@@ -133,7 +133,7 @@
   "missing-end-tags": "Missing end tags (%(name)s).",
   "unexpected-start-tag-implies-end-tag":
       "Unexpected start tag (%(startName)s) "
-      "implies end tag (%(endName)s).",
+          "implies end tag (%(endName)s).",
   "unexpected-start-tag-treated-as":
       "Unexpected start tag (%(originalName)s). Treated as %(newName)s.",
   "deprecated-tag": "Unexpected start tag %(name)s. Don't use it!",
@@ -165,7 +165,7 @@
   "unexpected-form-in-table": "Unexpected form in table context.",
   "unexpected-start-tag-implies-table-voodoo":
       "Unexpected start tag (%(name)s) in "
-      "table context caused voodoo mode.",
+          "table context caused voodoo mode.",
   "unexpected-end-tag-implies-table-voodoo": "Unexpected end tag (%(name)s) in "
       "table context caused voodoo mode.",
   "unexpected-cell-in-table-body": "Unexpected table cell start tag (%(name)s) "
@@ -180,12 +180,12 @@
       "Unexpected end tag (%(name)s) in the table row phase. Ignored.",
   "unexpected-select-in-select":
       "Unexpected select start tag in the select phase "
-      "treated as select end tag.",
+          "treated as select end tag.",
   "unexpected-input-in-select":
       "Unexpected input start tag in the select phase.",
   "unexpected-start-tag-in-select":
       "Unexpected start tag token (%(name)s in the select phase. "
-      "Ignored.",
+          "Ignored.",
   "unexpected-end-tag-in-select":
       "Unexpected end tag (%(name)s) in the select phase. Ignored.",
   "unexpected-table-element-start-tag-in-select-in-table":
@@ -204,7 +204,7 @@
       " in the frameset phase. Ignored.",
   "unexpected-frameset-in-frameset-innerhtml":
       "Unexpected end tag token (frameset) "
-      "in the frameset phase (innerHTML).",
+          "in the frameset phase (innerHTML).",
   "unexpected-end-tag-in-frameset": "Unexpected end tag token (%(name)s)"
       " in the frameset phase. Ignored.",
   "unexpected-char-after-frameset": "Unexpected non-space characters in the "
diff --git a/pubspec.yaml b/pubspec.yaml
index b3cf488..e13c01a 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: html
-version: 0.13.4+1
+version: 0.13.4+2
 
 description: APIs for parsing and manipulating HTML content outside the browser.
 author: Dart Team <misc@dartlang.org>
@@ -9,7 +9,7 @@
   sdk: '>=2.0.0 <3.0.0'
 
 dependencies:
-  csslib: '>=0.13.2 <0.15.0'
+  csslib: '>=0.13.2 <0.16.0'
   source_span: '>=1.0.0 <2.0.0'
   utf: '>=0.9.0 <0.10.0'