Add the documentation to the sdist tarball.
Add the documentation to the sdist tarball.

Currently the documentation is not included in the sdist provided by
PyPi due to this missing Manifest line.

Lh4cKg/clint,nathancahill/clint,tz70s/clint,nathancahill/clint,wkentaro/clint,thusoy/clint,glorizen/clint,1gitGrey/clint,1gitGrey/clint,kennethreitz/clint,wkentaro/clint