Add more array expressions.

[mrocklin]

Add TensorDot and Transpose expressions. Also fix shape handling and enforce dshape validation on binary operators.

In [1]: from blaze import *

In [2]: x = symbol('x', '10 * 20 * int')

In [3]: y = symbol('y', '20 * 30 * int')
In [4]: x + y
ValueError: Shapes don't align, (10, 20)

In [5]: x.dot(y)
tensordot(x, y)

In [6]: y.T
transpose(y)

[mrocklin]

@cpcloud this could use your review.

[cpcloud]

reviewing now

[cpcloud]

what's the reason for this? maybe do assert result.dshape instead just indicate that this needs to be run

[mrocklin]

For various reasons I don't like putting logic into the type constructors. Most of the logic is checked however when running dshape. Calling assert would work if the comment isn't sufficient to demonstrate intent.

[cpcloud]

people are going to start asking for a solve interface now :)