Type a fixo

adatpter -> adapter
Merge pull request #106 from knewter/patch-1

Type a fixo
Minor typo fix

`deps` should be a private function, I'd guess, since mix makes it so by default.
Merge pull request #107 from knewter/patch-2

Minor typo fix
Update postgrex
Use 'optional: true' for postgrex

This ensures that postgrex will be compiled before ecto for users
depending on ecto.
Fix an error in the Repo docs
Merge pull request #110 from knewter/fix-query-documentation

Fix an error in the Repo docs