Docs Makefile additions, compute/numpy tests.

Fixes the problem of capabilities.py failing to create the graph the first time docs are built on a machine. Simple fix. Also, there are some tests and random changes to compute_numpy in here that I added in. Going to remove the other pull request. @mrocklin @cpcloud 
In this case I get this error when I write the test this way: `AttributeError: 'bool' object has no attribute 'all'`

If I do it the other way, with all(x == y) I get another error: `TypeError: 'bool' object is not iterable`

This is the same with the other test. The only way I could think of to get it working was to iterate through both of them.