Added license section

Added license section and link to license file.
Fix display of block number in web view; block number is now correctly decoded from the coinbase of a share regardless of its size.
Update Python virtual environment to latest version (fixing an SSL pip vulnerability), and update build instructions to better cache the generated virtual environment.
Update development and testing dependency versions.
Merge pull request #228 from maaku/parse-bip34

Fix display of block number in web view
Merge pull request #229 from maaku/update-virtualenv

Update virtualenv and development/testing dependencies, restructure Makeflie
Merge pull request #217 from benhc123/patch-1

Added license section
Merge pull request #3 from forrestv/master

Merge latest changes from forrestv:p2pool