Load meta-schemas via pkgutil rather than searching the filesystem.
Load meta-schemas via pkgutil rather than searching the filesystem.

Hopefully this makes things like cx_Freeze work, but they appear to all be
special snowflakes and this doesn't appear easy to test.

Credit to @pjdelport for helping clear away some of the smoke.

Closes #161, #162

jamesmarva/jsonschema,mathewmarcus/jsonschema,eodolphi/jsonschema,varunarya10/jsonschema,Julian/jsonschema,dnephin/jsonschema,python-jsonschema/jsonschema,eodolphi/jsonschema,sightmachine/jsonschema,Julian/jsonschema