add some dependencies

this does not actually make `pip install imaginary` work :/
but perhaps the fix for the remaining issues is for epsilon, axiom, and mantissa to properly declare their dependencies?
I guess maybe.
Merge remote-tracking branch 'origin/master' into setup.py-dependencies
declare the transitive dependency on nevow
Also declare the transitive dependency on PyCrypto.
Add a couple more transitive dependencies.
Try setting up the test environment so ExampleGame is importable as well.
Perhaps travis-ci does not evaluate these using a shell?  Maybe the relative path will work.
Move one of the travis installation steps from the script section to the install section where it belongs.
Merge pull request #16 from exarkun/setup.py-dependencies

Declare Imaginary's dependencies in `setup.py` in a way pip can recognize.