Release 2.0.0 tasks

[nuwang]

Tasks outstanding for 2.0.0

Essential:
a. Make zone a part of the provider and remove it from all methods - we don't use multi-zone operations in general, so it seems like it's better to make it a provider wide setting, especially to benefit GCE. If at some point we want to perform multi-zone operations, we'll need multiple provider instances just like we do for regions or multiple clouds.
b. Prepare release note

Desirable but not essential:
c. Accept middleware in the provider constructor
d. Modify provider factory to pass in middleware
e. Consider whether it’s worthwhile moving config handling to ConfigProvider
f.Refactor GCE firewalls to use the Firewall object See: #194
g. Identify performance bottlenecks
h. Increase coverage > 90%

[nuwang]

Fixed in Cloudbridge 2.0.0