Exits via app.exit()
Exits via app.exit()

Calling app.exit() instead of process.exist() should force close
all open windows therefore making #56 superfluous.

As discussed in #60 closing all windows lead to Electron shutting
down with exit code 0 thus breaking CI tests etc. This could be
worked around by listening for the all-windows-closed event, but
I think this is the better solution.

jprichardson/electron-mocha,jprichardson/electron-mocha