check types with isinstance; allow tuple, where possible

[dizcza]

Dear Jack,

I stumbled upon a bad practice of checking the object type with type(x) == y. Also, a handy-used scenario is when the user populates a dict with keys as legend labels and values as the payload:

names, values = list(zip(*dict.items()))
viz.line(..., opts=dict(legend=names))

In short, legend sometimes can be passed as a tuple rather than a list, and I thought there is nothing wrong with allowing tuples.

How Has This Been Tested?

Tested by running the demo script.

Types of changes

• Other (non-breaking change which improves code readability)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• For JavaScript changes, I have re-generated the minified JavaScript code.

P.S. It ain't much, but it's honest work.
P.P.S. When I was fixing the bad practice here and there, I noticed some other small issues with the coding style like code duplication, old python usage, etc. At first, I felt tempted to dive deeply into fixing them all but noticed #675, which, of course, should be merged before any further sugar-code fixes.
P.P.P.S. One could set up Travis or CircleCI builds like I'm doing here to finally test the changes properly on each PR. I can write CircleCI build script if you set up a server.

Best,
Danylo

[JackUrb]

Style fixes are always appreciated! Definitely hoping to get #675 in sometime in the very near future as we prepare transitioning the project. And following that I'm hoping standardizing some CI for Visdom will be next on the docket. Happy to tag you with an up-for-grabs when we get CI set up.

As always, thanks for the contribution!