Removed R-code subdir, and updated index.rst with links.

This contributes to [Issue
211](https://github.com/biom-format/biom-format/issues/211).

https://github.com/biom-format/biom-format/issues/211
added extra colons
Merge pull request #214 from joey711/rm-R-biom

Removed R-code subdir, and updated index.rst with links.
Remove SparseDict and SparseMat backends

Also add hyperlinks to biom-format dependencies on index page.

Fixes #221. Fixes #205.
Update reference to biom.csmat
Merge pull request #224 from jrrideout/issue-221

Remove SparseDict and SparseMat backends
Remove python-code directory

Fixes #212.
Update setup.py and docs since python-code is gone
Merge pull request #225 from jrrideout/issue-212

Remove python-code directory
Add BSD license
Update doc license to BSD
Minor doc updates for new BSD license
Update copyright in source files
Update license in source files
Updated copyright in source files in some stragglers
Update copyright in sphinx conf
Update changelog with license change info
Update top-level source files with new header
Add header to biom/ source files
Add header to unit test source files