Move all inventory script code into the script parser
Allow inventory to be a directory containing other inventories
Make inventory basedir for directory based inventory be the directory

This puts host_vars and group_vars inside of the directory, allowing you
to target a single inventory but still have access to the variables.
vars_loader should get the path to the inventory + vars_plugins
Add some tests for directory-based inventory
Merge branch 'directory-inventory' of git://github.com/dhozac/ansible into devel
Disable filter test for now since it should really be testing at a lower level.