Fix missing passed parameters on some wrapped methods.
Add a wrapper for squeeze().

The numpy version ends up returning a Quantity with units set to dimensionless.
Wrap imag and real attributes.

This allows easily writing setter methods for them so that we can handle
units on set.
Fix use of call () on simplified.
repr special case for Quantity if magnitude.size == 1
add support for np.exp() to pq.umath