Add I/O recipe

Fixes #28. @gregcaporaso @ebolyen can you please review? [Link](http://nbviewer.ipython.org/github/jairideout/scikit-bio-cookbook/blob/io-cookbook/reading-and-writing-files-in-scikit-bio.ipynb) to rendered notebook.
*that can be serialized or deserialized* ->

*that can be serialized or deserialized (i.e., written to or read from a file)*