Limits/Offsets in Stacky API

Most Stacky API calls now have limit/offset query arguments.
The default limit is 50 and the hard limit is 1000.
Filter on when field for events in StackyAPI
Merge branch 'master' of git://github.com/rackerlabs/stacktach into stacky_refactor2

Conflicts:
	stacktach/stacky_server.py
Merge pull request #160 from ramielrowe/stacky_refactor2

Limits/Offsets and When Filter in Stacky API