Simplify Travis install phase.

Author: larsbrinkhoff

.travis.yml

@@ -14,9 +14,7 @@ before_install:
  - env | sort
 
 # Make sure CMake and Mono are installed
-install:
- - if [ "${TRAVIS_OS_NAME}" = "linux" ]; then ./CI/travis.linux.install.deps.sh; fi
- - if [ "${TRAVIS_OS_NAME}" = "osx" ]; then ./CI/travis.osx.install.deps.sh; fi
+install: ./CI/travis.${TRAVIS_OS_NAME}.install.deps.sh
 
 # Build libgit2, LibGit2Sharp and run the tests
 script: