build: COMPASS-3933: Fixing up deps

[imlucas]

• COMPASS-3933: Electron 6 updates
• Latest travis.yml template

fix: Update javascript-stringify

• Was being used as a transitive dep from query-parser which updated to javascript-stringify@2 causing test break

ci: use xvfb-maybe

Need to use https://npm.im/xvfb-maybe to configure the travis run for electron (needs a virtual buffer xvfb-maybe configures as needed)

> @mongodb-js/compass-schema-validation@3.1.0 test:karma /home/travis/build/mongodb-js/compass-schema-validation
> cross-env NODE_ENV=test karma start
START:
ℹ ｢wdm｣: Compiled successfully.
27 01 2020 22:57:26.260:ERROR [launcher]: Cannot start Electron
	
(electron:8394): Gtk-WARNING **: 22:57:26.250: cannot open display: 
27 01 2020 22:57:26.261:ERROR [launcher]: Electron stdout: 
27 01 2020 22:57:26.261:ERROR [launcher]: Electron stderr: 
(electron:8394): Gtk-WARNING **: 22:57:26.250: cannot open display: 
27 01 2020 22:57:26.313:ERROR [launcher]: Cannot start Electron
	
(electron:8407): Gtk-WARNING **: 22:57:26.311: cannot open display: 
27 01 2020 22:57:26.313:ERROR [launcher]: Electron stdout: 
27 01 2020 22:57:26.314:ERROR [launcher]: Electron stderr: 
(electron:8407): Gtk-WARNING **: 22:57:26.311: cannot open display: 
27 01 2020 22:57:26.364:ERROR [launcher]: Cannot start Electron
	
(electron:8417): Gtk-WARNING **: 22:57:26.362: cannot open display: 
27 01 2020 22:57:26.365:ERROR [launcher]: Electron stdout: 
27 01 2020 22:57:26.365:ERROR [launcher]: Electron stderr: 
(electron:8417): Gtk-WARNING **: 22:57:26.362: cannot open display: 
27 01 2020 22:57:26.365:ERROR [launcher]: Electron failed 2 times (cannot start). Giving up.
Finished in 0 secs / 0 secs @ 22:57:26 GMT+0000 (Coordinated Universal Time)