Modifies exp() and pow() and specs behaviour of z^inf and inf^z.

[harrysarson]

Previous behaviour was inconsistant and was not tested for. This commit ensures that z^inf and inf^z return reasonable and consistant values.

See #24 for the dicussion on the behaviour which can be summaried as:

z ^ Infinity === NaN
Infinity ^ z === Infinity if Im(z) === 0 and Re(z) > 0
Infinity ^ z === 0 if Re(z) < 0
Infinity ^ 0 === 1
Infinity ^ z === NaN otherwise

[harrysarson]

@infusion could you take a look?

[harrysarson]

@infusion I have solved the merge conflicts, would it be possible to review this?

[harrysarson]

@infusion any updates?