Update ttfautohint.rb with head

Added dependencies for building head, and added some commands needed for the bootstrap script to work, and removed the documentation (which requires pandoc which carries a huge amount of its own dependencies) 

cc @lemzwerg

>> @@ -18,10 +27,18 @@ class Ttfautohint < Formula
>>    depends_on "harfbuzz"
>>  
>>    def install
>> +    if build.head?
>> +      inreplace "configure.ac", "gnits", "gnu"
> 
> What's this for?

ttfautohint is using gnulib's `git-version-gen' module that derives
the version from the git repository.  Since Homebrew uses a source
code copy for compilation, `git-version-gen' doesn't return a version
but the string `UNKNOWN' instead.  Automake's `gnits' feature,
however, expects a valid version string, stopping with an error
otherwise.  Use `gnu' mode instead of `gnits' mode, this is no longer
a requirement and configuration succeeds

This is a hack, of course.  The documentation of `git-version-gen'
describes better solutions, but I'm not a Homebrew hacker to make this
work.

  http://git.savannah.gnu.org/cgit/gnulib.git/tree/build-aux/git-version-gen