Simplify migration calling, fix breakpoint use

Don't write to a temp file
Use `load_module` instead of `load_source`

This allows the use of breakpoints in IDEs and in pdb

Signed-off-by: Sandy Carter <sandy.carter@savoirfairelinux.com>
Merge pull request #50 from savoirfairelinux/breakpoints

Simplify migration calling, fix breakpoint use