Tests, Improvements and Bug Fixes

* Queue `clear` feature added
* Queue `close` feature added to close the redis connection when required
* Options access added. `q.options([option_key])`
* Assertions are made with `should`
* `mwq` prefix added to all queues because of name spacing
* `priority` tests added
* After hook added to clear all test queues
* README.md updated to indicate minimum redis version for Lua
* BUG_FIX: Redis keys were corrupted in some cases