Adds optional block argument to K::S::R.execute!

 - Furthers tests
More tests for Konamio::Sequence::Requisition object
Test passing a block to the Requisition object during execution
Merge pull request #4 from rthbound/further_tests

Code and tests for passing block to `Konamio::Sequence::Requisition.new.execute!`
Merge pull request #5 from rthbound/feature/optional_block

Feature/optional block