If you --ignore-scripts when installing electron currently, it'll fail
to write the path.txt file and thus fail to use the override dist path.
Open to other solutions - just hoping to be able to use a prebuilt
electron binary with the default package without having to muck around
with it installing an unused version.
* Provide an easy way to use a local build of Electron
For instance from ~/projects/electron/out/D
* document ELECTRON_OVERRIDE_DIST_PATH
* Make the linter happy
* Tweak ELECTRON_OVERRIDE_DIST_PATH docs
