memory-profiler: Convert to V8 Heap Dump

[keitwb]

This replaces the old output format in favor of a V8 Heap Snapshot
which is usable in Chrome Dev Tools.

This will hopefully be useful in debugging heap usage even though
it is not quite as full of metadata compared to the heap snapshots taken
from a normal V8 app.

This also adds the ability to export the heap snapshot to GEXF for use
in graphing tools like Gephi.

Also included is the ability to launch a REPL to manually explore the heap
graph.

Signed-off-by: Ben Keith keitwb@gmail.com

[coveralls]

Coverage remained the same at 94.25% when pulling 9b0f799 on keitwb:memory-profiler-v8 into bd2053d on Fitbit:master.

[Hexxeh]

I'll look into the CI error since I don't think it's related and get this merged, thank you! :)

[Hexxeh]

This should be good for a rebase, I've rebased and run yarn checkstyle -w to run the formatter on another branch and it all looks happy. I'd do it, but I don't think I have access to change the branch this PR is from. If you'd prefer I can do it for you in another PR and keep you in the commit author/signed-off?

[keitwb]

This should be good for a rebase, I've rebased and run yarn checkstyle -w to run the formatter on another branch and it all looks happy. I'd do it, but I don't think I have access to change the branch this PR is from. If you'd prefer I can do it for you in another PR and keep you in the commit author/signed-off?

Ok, I rebased.

[Hexxeh]

This should be good for a rebase, I've rebased and run yarn checkstyle -w to run the formatter on another branch and it all looks happy. I'd do it, but I don't think I have access to change the branch this PR is from. If you'd prefer I can do it for you in another PR and keep you in the commit author/signed-off?

Ok, I rebased.

You'll need to run yarn checkstyle -w as well to pass CI, there's normally a Git hook that does this automatically but I'm not sure why it hasn't run it in your case. Sorry about that!

[keitwb]

ok, yeah I think the hooks didn't run because I only did a rebase instead of a regular commit. Should be good now.