Support for JSON

Extracts string fields from a JSON document because hey, who doesn't love recursion? Suitable for text analysis of MongoDB dumps via mongoexport command. Output does not maintain / enforce any order of fields in an object, so the result should be used in bag-of-words modelling- n-gram algos beware. Also includes a small doc revision. All tests are passing on travis: https://travis-ci.org/anthonygarvan/textract. 

Also, the md5sum seems to be broken for the snow_fall.html example on Ubuntu 13.10 (fails for me locally but passes on Travis). Using OS utilities for this seems overkill - any reason not to use python's hashlib?