RGA subplot function and some pep8

Added a function to the existing RGA file that plots a subplot for each
element of the RGA matrix. Also changed some stuff in the file to be
pep8 compliant.
Reworked Example 2.3

Reworked Example 2.3 for transfer functions of any order
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Pythonificiation of some changes
Merge pull request #67 from clifford-oliphant/master

Corrected state controllability function in MIMO_Tools
Merge branch 'master' of https://github.com/alchemyst/Skogestad-Python
Automatic SISO multiplicative weight determination
Added function to automatically fit a third-order weight to a perturbed plant response. Currently only for SISO and assumes multiplicative uncertainty.
The function runs in perturbed_models as a script on the example system there.
Corrected uncomment of test function and moved routine to function
Corrected one-line docstrings
Created weight_calc function and moved routine there
Merge pull request #69 from SimonStreicher/master

Automatic SISO multiplicative weight determination
Mimicked step function in MatLab
Displays response of each element in a process transfer function matrix to a step input on a single figure with subplots arranged like elements in matrix.
steptest_models_tf.py is needed to demonstrate working of function
Merge pull request #70 from SimonStreicher/master

Step function implemented for tf objects
Merge remote-tracking branch 'upstream/master'
Added MIMO bound uncertainty bound calculation
Merge pull request #71 from SimonStreicher/master

Added MIMO uncertainty bound calculation
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' of https://github.com/alchemyst/Skogestad-Python
Pythonificiation of some changes
Added MIMO bound uncertainty bound calculation
Ex 6.8