Make README.md ReST-friendly

Description at PyPI looks ugly with all these hashes. Changed according
to https://gist.github.com/dupuy/1855764

Change-Id: I070a245d417cf36f115741418764630d053da476
Download specific Patch Set for Review

Adds ability to request download and checkout
of specific review-patchset using syntax:
 git review -d <reviewId>,<patchsetNumber>

It will create and checkout the <author>/<topic>-patch<number> branch.

Change-Id: Idaf57acb1464e1e71a436d741ae889494a91d446