Implement static_live_server (Django1.7)

fixes #120

<strike>WIP, not ready for merging
Documentation still need to be addressed</strike>
@blueyed You can have a look for testing with `testdir.runpytest()` approach on a new branch https://github.com/ticosax/pytest_django/tree/issue-120-2
I'm not completely convinced because It is more verbose, the settings are duplicated, test.compat can not be imported so the imports are copy/pasted, ... many small details that goes against practicality. Maybe all of this can be fixed ? tell me what you prefer.