Auto merge of #4686 - lzutao:fix-travis-windows-stuck, r=Manishearth

travis: Windows build might be stuck as non-supported languages

See <https://docs.travis-ci.com/user/reference/windows/#supported-languages>
for list of Windows supported languages.

I'm sorry for making Travis Windows build stuck.

changelog: none

Author: bors

.travis.yml

@@ -1,5 +1,5 @@
 dist: xenial
-language: minimal
+language: bash
 
 os:
   - linux