Profitbricks

Update includes the following:
- PB exception for rate limit exceeded.
- Removed broken download URL from setup.py.

This release includes the following changes.
- Added custom ProfitBricks errors as described in 6.
- Fix passing of mutable values as default arguments.
- Cleaned up example scripts.
- Apply flake8.

This updates the ProfitBricks SDK for Python to the ProfitBricks Cloud API v3. Changes include the following:
- Updated Cloud API REST URL.
- Added support for volume availability zones.
- Added support for NAT.
- Set `User-Agent` header with SDK name and version.
- Changed `Content-Type` to `application/json`.

Updates include the following:

Features
- Added support for volume `ssh_keys`.
- Added support for volume `image_password`.
- Updated README with new features.
- Cleaned up live tests.

Bug Fixes
- Convert disk size value to an integer (issue 38).
- Set `icmp_code` and `icmp_type` to strings to avoid zero/None conversion (issue 37).
- Added the `name` parameter to the create_ipblock() method.
- Set default test location to `us/las`.

Minor updates including:
- Added support for server cpuFamily.
- Added example scripts to add, delete and power on/off servers.

- Bugfixes for creating NIC, Loadbalancer, LAN.
- Extended description of methods in folder examples.
- Bugfixes to profitbricks/client.py.
- Bugfixes to examples/pb_datacenter_inventory.py.
- Changed format of examples/pb_datacenter_inventory.py from DOS to UNIX.
- Extended tox.ini by config parameters for pep8 and flake8.
- Applied flake8 rules to examples/pb_datacenter_inventory.py and setup.py.
- Add command line parameter '--datacenter' as an alias for '--datacenterid' in examples/pb_datacenter_inventory.py.
- Made examples/pb_datacenter_inventory.py executable.
- Adding *.csv to .gitignore.
- Experimental Dockerfile for running live tests.