Initial revision of code. Importing and drafting.
* diff_match_patch.py:
  * Imported from Google's implementation. Apache v2.0 code by Neil Fraser.
* dsync.py:
  * Sketching out the Differential Synchronization algorithm by Neil Fraser.
  * Laying ground work for multi-method peer management
  * Based in part on HTTP code from Mailpile
  * Not actually working yet.
Added some tests and cleanups. It appears to... work.