Python 2.6 is required for gyp

Document the problem (http://stackoverflow.com/questions/21155922/error-installing-node-gyp-on-ubuntu) and suggest a solution (use a Python version manager eg pyenv). This is especially helpful for Ubuntu 14.04 which comes with Python 2.7.
Merge pull request #597 from ethers/master

Python 2.6 is required for gyp
add Passphrase test
add more test coverage for Wallet
add coverage, skip failing tests
Merge pull request #602 from maraoz/add/tests

add tests, and skip failing ones
update to peerjs 0.3.8. use bower dist
simply a little webRTC error handling, add more messages
fixing tests
fix tests