Implement a statement cache of 100 requests

Fixes issue #10:
* 1-line code change is from user billywhizz
* Avoid compiling the SQL in the client every time you execute a statement
* This adds a statement cache with hardcoded size of 100; may want to make configurable at some point
Merge pull request #142 from mwolson/t-statement-cache

Implement a statement cache of 100 requests