Performance: V8 snapshots

[bryphe]

Atom had an interesting strategy for improving startup performance in their blog post here:
http://blog.atom.io/2017/04/18/improving-startup-time.html

They are leveraging V8 snapshots to output a JS heap. This saves all the parsing and processing of JS, which is non-trivial as the bundle.js for this project gets larger.

There are some restrictions (V8 snapshots run in a bare V8 context), so it's important to have solid testing to ensure we aren't breaking anything in these cases.

[bryphe]

One possible avenue to help with #355, but improving the real startup performance.

[bryphe]

One suggestion that @bruchmann made on #1123 was leveraging electron-link to accomplish this. Would be interesting to see how straightforward this is to plugin to our infra/build.

[bryphe]

mksnapshot seems to be used as well