[Travis] Install Mercurial

.travis.yml

@@ -3,7 +3,9 @@ env:
   # This is what 10.8.x comes with and we want to support that.
   - RVM_RUBY_VERSION=system NOEXEC_DISABLE=1 RUBY_VERSION_SPECIFIC='sudo gem update --system && sudo gem install bundler --no-ri --no-rdoc' GIT_AUTHOR_NAME=CocoaPods GIT_AUTHOR_EMAIL=cocoapods@example.com
   - RVM_RUBY_VERSION=1.9.3 NOEXEC_DISABLE=1 RUBY_VERSION_SPECIFIC='sudo ln -s /usr/bin/llvm-gcc-4.2 /usr/bin/gcc-4.2 && curl http://curl.haxx.se/ca/cacert.pem -o /usr/local/share/cacert.pem' SSL_CERT_FILE=/usr/local/share/cacert.pem GIT_AUTHOR_NAME=CocoaPods GIT_AUTHOR_EMAIL=cocoapods@example.com
-before_install: source ~/.rvm/scripts/rvm && rvm use $RVM_RUBY_VERSION
+before_install: 
+  - source ~/.rvm/scripts/rvm && rvm use $RVM_RUBY_VERSION
+  - brew install mercurial
 install: eval $RUBY_VERSION_SPECIFIC && rake bootstrap[use_bundle_dir]
 script: bundle exec rake spec:ci
 notifications: