Whoops. Forgot to touch this __init__.py.
Merge branch 'master' into add_setup

Merging in a fix for making tests/ part of the package properly.
Add setup.py

Added a basic setup.py for the project. Not a lot of metadata, just
grabs the packages so far.
Merge branch 'add_setup'

add_setup added a simple setup.py. This is in preperation for making this
codebase use tox for tests.
Added tox.ini to the repostiory.
Merge branch 'tox_setup'

Copied a tox.ini file into the package. Need to fix old names used in the
tests and we should be back to full-passing tests.
Add import statements to core's __init__.py.

Throwing these imports in here so you can avoid having to type
'interval' too many times.
Implement xor operator for Interval types.

I've leveraged the xor (^) for determining whether two intervals
intersect. Trying to include an intersection check on <= is too much
when you can simply use `if a < b and a ^ b` to check if the ranges
are sequential (a precedes AND overlaps with b).
Reorganized imports in the tests.
Intersect comparions now use the ^ operator instead of <=.