Refactor graph code

[tonysyu]

Sorry, this is a bit of a code dump, but I tend to refactor code when I'm trying to understand it. I completely understand if this is too massive a change for merging.

Note that PStatRow is renamed to PStatsNode, while PStatGroup and PStatLocation are removed. The latter was unused and the group was only used temporarily to package multiple PStatRows, but only the first is ever used.

Other changes:

• Add user-specified tree-depth for upload. This is a work around for issue Improve large profile handling #12.
• Tests! And Travis CI
• I've added a comment about some weird loop-back behavior in stats_to_tree_dict. Basically, when the size of child calls doesn't add up to the parent size, the parent is linked to itself. I don't understand what this is trying to accomplish, but I didn't want to remove it (since I didn't understand it).

[embray]

Thanks for this! I'll have to take a closer look at it later.

IIRC the pstatsloader module came directly out of runsnakerun (with permission) hence parts of it seeming unused/superfluous. As such I'm a little hestitant to go removing/changing things in there unless there's some marked improvement in doing so.

It looks like you also changed optparse to argparse which I wholly support. I'm not sure why it wasn't using argparse (possibly for support of older Python versions at the time).

[jiffyclub]

Thanks for having a go at improving snakeviz! Updating snakeviz has finally floated to the top of my to-do list, and there are major changes coming. In particular I'm planning to remove almost all the Python business logic and re-implement it in JavaScript on the client side (e.g. #19, but not exactly reimplementing pstatsloader). So, unfortunately, my plan is to delete almost everything you've changed here. 😬

But, I don't have my update working yet, so if we wanted to use some of this in the meantime I would be okay with that.

BTW @tonysyu, the reason we add add a child linked back to the parent is to represent the internal time in a function, e.g. time not spent inside other functions. I seem to remember that the visualization came out funky if we didn't do that.

[tonysyu]

Thanks for the reply! No worries, if this goes in the waste bin. I was actually refactoring because I was thinking of taking a go at the JS conversion, but I wanted to figure out how the Python code actually worked. If this part of the code is going to be tossed in the near future, feel free to close this.

[jiffyclub]

I've put up #42 with a version 0.2 release candidate, please feel free to have a look at that and see if it works for you.