Datastore is now an interface using the abc module without the need of NotImplementedErrors
Merge pull request #985 from carolinux/cleanup-abc

Datastore is now an interface using the abc module
Update Mac install script

* Always brew install python.
* Explicitly set virtualenv executable.
* Drop pip installation; installing python via brew has us covered.
* Warn the user of potential connectivity problems when UPNP fails.
* Add autoenv support for mac
* Always activate our virtual environment
* Only on mac, tell users to run openbazaar with --disable-sqlite-crypt
donation address, pass, notary
Merge pull request #972 from tikhon/mac

Update mac configuration