Clean up benchmarks
Greatly improve performance by removing TestOnBorrow.
I removed the TestOnBorrow option from the redigo pool.
The purpose was to manually check the health of a borrowed
(idle) connection with a PING command.
I don't believe it's necessary, since problems with a conn
are very rare (all the tests still pass).
Even in the rare case of a bad connection, zoom will return an
error and let the user know what happened. Making this change
results in nearly a 2x performance increase for direct redis commands
like PING, SET, and GET. The performance increase is most noticable
in the Save, Delete, and FindById methods, where testing the borrowed
connection was taking up a significant portion of time.