Run non-strong analyzer on travis (dart-lang/stream_transform#15)

Fixes dart-lang/stream_transform#14

pkgs/stream_transform/.travis.yml

diff --git a/pkgs/stream_transform/.travis.yml b/pkgs/stream_transform/.travis.yml
index 4c02d8e..1d18a7e 100644
--- a/pkgs/stream_transform/.travis.yml
+++ b/pkgs/stream_transform/.travis.yml
@@ -11,6 +11,7 @@
   - test
   - dartfmt
   - dartanalyzer
+  - dartanalyzer: --no-strong .
 matrix:
   exclude:
     - dart: 1.22.1