Temporarily disable travis on linux

Summary: Travis is broken on linux, disable it temporarily

Test Plan: https://travis-ci.org/facebook/rocksdb/builds/137721712

Reviewers: yhchiang, kradhakrishnan, sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D59673

.travis.yml

@@ -1,7 +1,7 @@
 sudo: false
 language: cpp
 os:
-  - linux
+#  - linux
   - osx
 compiler:
   - clang