Move keyword query building to separate file
Add query pretty printing

Closes #224.
Use pessimistic versioning for poolboy on minor instead of patch level, bump ex_doc to 0.6
Merge pull request #288 from rbishop/master

Bump versions of poolboy, decimal and ex_doc dependencies
Add select to query inspect
Handle type tagged values in query inspect
Remove : after from when inspecting query
Don't bind source unless necessary