Refactoring based on existing add_pool tests.
stab at #111: refactored add_pool/8, add_pool/9 to use add_pool/2 instead of the other way around; added some tests for type correctness; updated tests that use add_pool/8/9 to use add_pool/2 and deprecated old tests
Merge branch 'master' of github.com:Eonblast/Emysql
Merge pull request #122 from jkingsbery/master

add_pool/k for k>2