Multiple changes to improve compatiblity with python3

[dilawar]

• removed some python3 incompatible statements.
• Fixed some test scripts.
• python3 does not accept float as index. Converted indices to int in many places.
• Minor tweaks to some functions for passing plotting arguments such as color, alpha etc esp. in phaseplane.
• scipy 1.x compatible (this is from @tkf ).

[Silmathoron]

Hi there, this PR seems very useful (I just had to hack the whole scipy part myself).
Is there something specific preventing it from being merged? (except for the necessary pull from master?)
Is it possible to help with this in any way?

[z2v]

@Silmathoron Most changes have been already merged to master. I'll take a look and cherry-pick whether there are more changes.

[Silmathoron]

Ok, that's good to hear! I was using the PyPi version so I'll probably just switch to master, thank you

[coveralls]

Coverage remained the same at 11.311% when pulling f48b6ef on dilawar:master into 45fc2f1 on robclewley:master.