CLN: Change bare exceptions pt 1
Relates to #3954. In addition to changing exceptions types returned to be more explicit, this pull incorporates the following changes:
1. Adds a new `assertRaisesRegexp` to `util/testing.py` to port the `assertRaisesRegexp` helper from 2.7+ unittest
2. Cleans up stats/common.
3. Fix up initial assertions in `tseries.offset._cached_range` that were all off + fix the test cases which were all just raising TypeErrors because they were calling with the wrong arguments.
4. Changes the example timezone from Asia/Beijing to Asia/Hong+Kong b/c `Asia/Beijing` is not supported by pytz.
5. Any tz-aware : tz-naive comparison fails with TypeError, as will mismatched, localize, etc. calls.
6. Changes `SparseArray` indexing error messages to match tuple message for completeness.
7. Improves the window check in ols.

After you all say it's okay to merge, I'll update the docs to reflect changes.
