add shortcut for from p in __MODULE__
Allow all query expressions where only fields was allowed

`order_by`, `group_by` and `distinct` now allow all forms of query
expressions instead of only allowing lists of fields.
Merge pull request #235 from jw2013/master

add shortcut for from p in __MODULE__
Bump Hex requirement in README
Remove expansion of variable to fields outside of select

Closes #236.
Check for grouped expressions in order_by and distinct
Import `Ecto.Model.scoped/2`
Update changelog
Aggregate functions will group query
`parse_url` should be less restrictive
Properly align code sample in validations
Remove teardown in favor of on_exit
Remove deprecated conversion functions
Merge pull request #240 from pma/master

Remove deprecated conversion functions
Remove unnecessary on_exits
Release v0.2.1
Bump to v0.2.2-dev
Fix size/1 warning
Fix compile error on elixir master
Fix more compile errors