* Rename `calc` to `math eval` and allow it to optionally take the expression as an argument
* Moved calc tests to math eval
Also added 2 tests and changed 1 test
* Move calc docs to math eval
* Move sum tests into math directory
* Move sum documentation over to math documentation
One sum example already existed in the math examples and a few of the others were outdated and didn't work, so I only moved one over, and updated their output
* Remove no-longer-in-use mod statement