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)
Yeah, I don't think you need it:

```
In [3]: from sympy import Matrix

In [4]: Matrix([1, 2, 3])
Out[4]: 
Matrix([
[1],
[2],
[3]])
```