misc: enable and fix a number of lints (#60)

diff --git a/analysis_options.yaml b/analysis_options.yaml
index e9b4026..63c0b90 100644
--- a/analysis_options.yaml
+++ b/analysis_options.yaml
@@ -2,19 +2,23 @@
   strong-mode:
     implicit-casts: false
   errors:
-    unused_import: error
-    unused_local_variable: error
     dead_code: error
     override_on_non_overriding_method: error
+    unused_element: error
+    unused_import: error
+    unused_local_variable: error
 linter:
   rules:
+    - always_declare_return_types
     - annotate_overrides
     - avoid_empty_else
     - avoid_function_literals_in_foreach_calls
     - avoid_init_to_null
     - avoid_null_checks_in_equality_operators
+    - avoid_renaming_method_parameters
     - avoid_return_types_on_setters
     - avoid_returning_null
+    - avoid_types_as_parameter_names
     - avoid_unused_constructor_parameters
     - await_only_futures
     - camel_case_types
@@ -34,6 +38,7 @@
     - library_names
     - library_prefixes
     - list_remove_unrelated_type
+    - literal_only_boolean_expressions
     - no_adjacent_strings_in_list
     - no_duplicate_case_values
     - non_constant_identifier_names
@@ -48,6 +53,7 @@
     - prefer_conditional_assignment
     - prefer_const_constructors
     - prefer_contains
+    - prefer_equal_for_default_values
     - prefer_final_fields
     #- prefer_final_locals
     - prefer_initializing_formals
@@ -70,4 +76,5 @@
     - unnecessary_statements
     - unnecessary_this
     - unrelated_type_equality_checks
+    - use_rethrow_when_possible
     - valid_regexps
diff --git a/example/web/main.dart b/example/web/main.dart
index 9c63f30..aa566c3 100644
--- a/example/web/main.dart
+++ b/example/web/main.dart
@@ -7,7 +7,7 @@
 // ignore: uri_has_not_been_generated
 import 'package:webdev_example_app/app_component.template.dart' as ng;
 
-main() {
+void main() {
   // ignore: argument_type_not_assignable
   runApp(ng.AppComponentNgFactory);
 }
diff --git a/webdev/test/integration_test.dart b/webdev/test/integration_test.dart
index 728f779..4be91a0 100644
--- a/webdev/test/integration_test.dart
+++ b/webdev/test/integration_test.dart
@@ -245,8 +245,8 @@
 const _supportedWebCompilersVersion = '0.4.0';
 
 String _pubspecLock(
-    {String runnerVersion: _supportedBuildRunnerVersion,
-    String webCompilersVersion: _supportedWebCompilersVersion}) {
+    {String runnerVersion = _supportedBuildRunnerVersion,
+    String webCompilersVersion = _supportedWebCompilersVersion}) {
   var buffer = new StringBuffer('''
 # Copy-pasted from a valid run
 packages: