Removing callbacks and binds where unnecessary

Hello eford, 

Please review the following commits I made in branch 'azulus-callbacks'.

ca8e88efdf4bf7125994eea55757a2d64e672f5d (2013-04-15 15:35:59 -0700)
Removing callbacks in favor of contexts

51bb32161a05ae81ce181dd985d930d94a0c3f7b (2013-04-15 15:21:03 -0700)
Flipped ConnectionPool to use promise contexts

R=eford