Added support for custom user models
Merge commit '205229fc81bc5f8580ec9a742965db046fce2d79'

Conflicts:
	README.md
	hijack/admin.py
	hijack/helpers.py
	hijack/views.py

used django compat for the imports
fix

admin: don't user username because of custom models
views: delete User import
update readme

support for custom user models
readme

compatibility for django 1.4 - 1.7
Merge pull request #20 from yannik-ammann/master

merged commit 205229f, implemented django-compat and performed tests
thank you guys, looks good!