adds --help and usage info
removes nltk dependency

Handy and fun, but WordNetLemmatizer requires
corpus download, which requires nltk_data folder
locally, which is a lot of overhead.

Squashed commit of the following:

commit 1ecd198bb0fc901442c98a40774e2e5c9503323e
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Thu Mar 13 23:00:06 2014 -0400

    removes references to ntlk from README

commit a94f854cc471e871f0ec734079310b70ec4e4e7e
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Thu Mar 13 22:59:53 2014 -0400

    removes nltk requirement

commit 160a1a1b72d057f0dd4096de01fcb084c51d1c61
Author: Conor Schaefer <conor.schaefer@gmail.com>
Date:   Thu Mar 13 22:59:36 2014 -0400

    removes nltk imports