MAINT: Clean up unused data in test.
MAINT: Adding tests for Blotter handling of limit and stop orders.

Adds a test algorithm that tries to buy with very high limit prices/very low
stop prices and tries to sell with very low limit prices/very high stop prices.
BUG: Fix a bug causing us to discard very low limit prices.

Fixes an issue where very low limit prices were being rounded to 0.0 and
effectively resulting in market orders.  Adds an explicit check to test for
this behavior.