Added rereddit.comment function.
See example usage below.

    rereddit.login('username', 'password').end(function(err, user) {
      rereddit.comment(parent, text).as(user)
        .end(function(err, res) {
          console.log(res.errors === [] ? 'Sucess' : 'Failure');
        });
    });
Merge pull request #2 from zachfogg/master

Functionality for posting comments.