Added scribe

New formula for CMake fork of https://github.com/facebook/scribe
Ideally we'd use original the autotools version. However:
1) it's broken on automake 1.14 https://github.com/facebook/scribe/pull/75
2) has no version zip/tarball for us to use
3) depends on fb303, which is not available from the current thrift formula
The CMake fork however works: https://github.com/onlinecity/scribe

Should be included because having a local scribe server helps developing services that assume one is running.