Add evewho.com api
Few code corrections in eve_who.py
Fixed calculating pages for member count divisible by 200
Add subclass for exception fetch error in evewho api.
Merge pull request #128 from l0ser140/evewho

Add evewho.com api
Streamlining the get method.

- No more multiple path flows for three different cases, at the cost of
  having to parse the XML tree again for subsequent calls.
- Test data should return meaningful results as it's possiblt to verify
  whether the sentinel object was called.  This ensures calls don't die
  on unexpected values.
- Test responses modified to return consistent values as it would be in
  a real call.
- Remove bad cross breeding of code from other branch.
Record the last timestamps used.

- Define a private method to facilitate this.
Description for the mocks.
Merge pull request #132 from metatoaster/streamline_get

Streamline the get method
Invalidate old cache keys for caching changes

Since we're now storing the XML documents in the DB rather than the parsed objects, we should invalidate any existing keys to prevent crashes.