nosebook-setup: configuration of scripts to run before cells

[bollwyvl]

From @gramster on #12 about this line:

The startup script is because we have a config.py that gets loaded in our environment and I need to load that in the test environment too (it contains just a single import in our case).

I suggested going with the nosebook-like setup.

Additionally, it seems like accepting a dotted-notation module may be more nose-like than a path.

initial configuration would be like:

nosetests --with-nosebook --nosebook-setup=scripts.setup_environment

and then i guess scripts.setup_environment would be loaded in the kernel: if importing that module has side effects, so be it!

Borderline YAGNI, It may be desirable to implement like scrubs, where the argument can be either:

• a string as above
• a list of strings, to import in order (somewhat unnecessary)
• a dict of notebook patterns to a string or list