Basic vector code, without a coordinate system class

All calculations essentially occur in the same frame.
i, j, k and x, y, z are imported as base vectors and base scalars by default on importing sympy.vector.
delop is a Del operator instance.

Example:

>>> v = 3*i - j
>>> delop ^ v
0

(delop ^ v represents curl of v)
Please try to make your docstrings for public methods a bit more detailed. I'd recommend loading the `__doc__` attribute from the methods your a mimicing at least. But complete sentences with proper punctuation should be the norm. Also follow the numpydoc format for describing the args and kwargs, examples, notes, etc.