Prevent emulator from hanging from requiring user code that doesn't exit.

[laurenzlong]

This fixes the bug where the emulator hangs when there's something within the functions source code that causes the process to not exit. For example, if someone has the following lines at a global scope (outside of exported functions):

var firebase = require('firebase-admin')
firebase.initializeApp(...);
var databaseRef = firebase.database(); // this opens up a connection to the database, which forces the process to not exit.

The set timeout is there since otherwise there may an issue with console.log not displaying the full output due to not having enough time to clear the buffer.

[codecov-io]

Codecov Report

Merging #103 into master will decrease coverage by 12.4%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           master     #103       +/-   ##
===========================================
- Coverage   77.36%   64.96%   -12.41%     
===========================================
  Files          52       52               
  Lines        2129     2129               
===========================================
- Hits         1647     1383      -264     
- Misses        482      746      +264

Impacted Files	Coverage Δ
src/cli/controller.js	75.4% <100%> (ø)	⬆️
src/model/functions.js	18.25% <0%> (-51.46%)	⬇️
src/supervisor/supervisor.js	35.03% <0%> (-36.62%)	⬇️
src/service/rest-service.js	54.54% <0%> (-35.36%)	⬇️
src/utils/errors.js	50.9% <0%> (-16.37%)	⬇️
src/model/cloudfunction.js	84.9% <0%> (-3.78%)	⬇️
src/model/operation.js	86% <0%> (-2%)	⬇️
src/model/protos.js	80% <0%> (-1.82%)	⬇️
src/cli/commands/delete.js	88.23% <0%> (+2.94%)	⬆️

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[jmdobry]

Published in 1.0.0-alpha.19

[laurenzlong]

Thanks for the speedy merge and publish @jmdobry !