Builtin snippets are not working when the snippets package is loaded from a V8 snapshot

Prerequisites

[x] Put an X between the brackets on this line if you have done all of the following:
- Reproduced the problem in Safe Mode: http://flight-manual.atom.io/hacking-atom/sections/debugging/#using-safe-mode
- Followed all applicable steps in the debugging guide: http://flight-manual.atom.io/hacking-atom/sections/debugging/
- Checked the FAQs on the message board for common solutions: https://discuss.atom.io/c/faq
- Checked that your issue isn't already filed: https://github.com/issues?utf8=✓&q=is%3Aissue+user%3Aatom
- Checked that there is not already an Atom package that provides the described functionality: https://atom.io/packages

Description

When the snippets package is loaded from a V8 snapshot, I think __dirname doesn't point to the correct directory and this code: lib/snippets.coffee:80-85, fails to find the correct path to the bundled snippets.{cson,json}.

Might have to pull off something like this atom/github/lib/helpers.js:7-21 for this to work. Though someone might want to refactor so as to reuse the logic rather than copy it at some point.

This is particularly jarring since it is mentioned right there in the default snippets.cson and in Atom Flight Manual – Snippets.

Note that it does work in dev mode which skips the V8 snapshot

Steps to Reproduce

Open your snippets.cson in your .atom.
Type snip<tab>

Expected behavior: The builtin "snip" snippet is expanded.

Actual behavior: It's not expanded.

Reproduces how often: 100%

Versions

Windows 10.0.15063 x64

Atom    : 1.20.1
Electron: 1.6.9
Chrome  : 56.0.2924.87
Node    : 7.4.0

apm  1.18.4
npm  3.10.10
node 6.9.5 x64
python 2.7.14
git 2.14.1.windows.1
visual studio 2015

atom / snippets