use `time.clock` for python versions older thatn 3.3
manually pop items from list when no `clear()` is provided
install mock for python version 3.2
add python version 3.2
read requirements for py32
factory pattern for sourcing modules
raise OSError instead of FileNotFoundError when not supported
use `__name__` when `__qualname__` not supported
renamed sourcer package to loaders
use try-except clause instead of `sys.version_info`

This adds support for newer python versions.
renamed sourcer to loaders
tested loaders for all python versions >= 3