Added text howtows.
Added packe and unpack
Update and rename sarray_corpus.py to sarray_vocabulary.py
Update README.md
Update sarray_vocabulary.py

Made it within 80chars
Update sframe_pack.py

Made within 80 chars
Update sframe_unpack.py

Made within 80 chars
Merge branch 'master' into text-howtos

Conflicts:
	README.md
Merge branch 'text-howtos' of https://github.com/graphlab-code/how-to into text-howtos

Conflicts:
	README.md
Merge pull request #6 from graphlab-code/text-howtos

Text howtos
Update README.md
Add a contributing guideline document.
Merge pull request #8 from znation/styleguide

Add a contributing guideline document.
fix URL of contributor guide
Use absolute URL for contributing link

Code reviewed over shoulder by Rajat.
Add example of making a cross product of parameter values.
This patch contains three how-to related to datetime:

1)How to convert a datetime column to string and back again to datetime
2)How to convert a datetime column to unix timestamp
3)How to split datetime column into multiple column
Added image_converter how-to

Made a how-to detailing how to convert graphlab images to PIL images,
rotate them, and convert them back. Put this in an apply function.
Split up to_pil and from_pil into 2 how-tos
Addressed Zach's comments on how-to's