Updated EggDiscovery documentation.
Merge pull request #197 from aloysbaillet/update_eggdiscovery_doc

Updated EggDiscovery documentation.
Deleted unnecessary import. Should fail in travis!
travis now installs nose2 instead of setting PYTHONPATH=.
Move nose2 into new src folder.

This is to avoid relative import when running tests in top folder.
This fixes some issues when running functional tests which change the
current folder and make late import of nose2 modules impossible.
tox and travis are now running the same exact commands.
Using setup.py develop to allow support files to be found