v2016.04.18.01

Release

Thanks to @Dominator008, vm_args was added to java_test documentation: https://buckbuild.com/rule/java_test.html
xctests are now streamed to Buck instead of waiting until completion
A flatten_dicts method was added for use in build files: https://buckbuild.com/function/flatten_dicts.html
Buck can now fail the build when using header files that are untracked by build files: https://buckbuild.com/concept/buckconfig.html#cxx.untracked_headers
Buck now has very basic support for the AppleTV platform
Buck now caches its Action Graph, which is part of the Parsing phase. Large projects should see this step speed up.
Cross-cell references can now be called with @ or +. The latter is useful for command-line invocations.
The repl command was added: https://buckbuild.com/command/repl.html
Support for Android NDK r11 and newer was added.
Buck now allows overriding of the command to package for apple_binary rules: https://buckbuild.com/concept/buckconfig.html#apple.*_package_command