Multiple changes

* Use mediafire: URI
* Rename ChunkedFileWrapper to SubsetIO
* Rename project to python-mediafire-sdk (got OK from MediaFire)
Add purge calls
Rename internal functions, add purge support
Add argument subparsers, update client calls
pep8 style fixes
list_folder -> get_folder_contents
Update README
Fix folder_create
Back to group_method

Separate API nodes brought no benefit and increased complexity.
Fix debug output
Work around resource removal breaking signature
Multiple changes

* API: Fix file_update in API
* API: Fix folder_key usage in uploads
* Client: Allow anonymous usage
* Client: Rename actions
* Client: Add file-update-metadata, folder-update-metadata actions
* SubsetIO: Add StringIO test
* Update README
Add Content-Type header to request
Fix upload to folders that don't exist yet
Do basic validation for upload/download args

Also:
* Use router for function calls
* Use built-in argparse way of handling positional arguments
Don't use multipart encoding for upload/simple

http://forum.mediafiredev.com/showthread.php?145
Specify required dependency versions. Fixes #1