These refactoring and conversion tools are based on pfff instead of the core
hh_server code due to pfff's superior support for parsing, modifying, and then
unparsing PHP code. However, this makes them more annoying to build.

To install:

1) Install OPAM (http://opam.ocaml.org/doc/Quick_Install.html)
   Don't forget to run "opam init"
   Don't forget to run "eval `opam config env`"
2) Install pfff (opam install pfff)
3) For each tool you want:
   cd $TOOL
   make clean && make depend && make
3) Binaries are installed at hack/bin/tools, where hack is the directory for
   this repo
