Added tensor_contract function to tensor.py.
Fixes for Python 3 and unit tests.
Added support for colormaps to Hinton diagrams.

This should help provide accessibility support, as the red/blue
colormap can be difficult to impossible to read for colorblind users.
Added superoperator support, colorblind mode to hinton().
Added colorblind_safe setting.
tensor_contract now preserves superrep by default.
Added fallthrough case for to_super to catch bugs elsewhere.
New label support for hinton().
Merge remote-tracking branch 'upstream/master' into feature-tenscontract

Conflicts:
	qutip/operators.py
Added docstrings to _isqubitdims and _cb_labels.
initial work on refactoring parallelization of mcsolve to use qutip.parallel.parallel_map
remove commented code
support storing expectation values and states
fixed progressbar with parallel_map in mcsolve
resolved merge conflict
Merge remote-tracking branch 'origin/parallel-updates' into refactor-mcsolve-parallel
remove unnecessary warning
code cleanup, use num_cpu spec in options for parallel_map. fallback to serial_map if num_cpu is 1
code cleanup. unified styles
Merge branch 'master' into refactor-mcsolve-parallel