Updated travis to xcode 7

.travis.yml

@@ -1,5 +1,5 @@
 language: objective-c
-osx_image: beta-xcode6.3
+osx_image: xcode7
 before_install:
     - gem install cocoapods --no-rdoc --no-ri --no-document --quiet
     - gem install xcpretty --no-rdoc --no-ri --no-document --quiet