Fix travis test (#26) 🎉 🎉

Author: tvc12

.travis.yml

@@ -8,9 +8,8 @@ addons:
       - ubuntu-toolchain-r-test # if we don't specify this, the libstdc++6 we get is the wrong version
     packages:
       - libstdc++6
-      - fonts-droid
 before_script:
-  - git clone https://github.com/flutter/flutter.git -b beta
+  - git clone https://github.com/flutter/flutter.git -b v1.9.1+hotfix.6
   - export PATH=`pwd`/flutter/bin:`pwd`/flutter/bin/cache/dart-sdk/bin:$PATH
   - flutter doctor
 script: