Update from upstream repo CachetHQ/Cachet (#5)

* System status now ignores hidden groups for guests - Fixes cachethq#2577

* Fix typo

* Update deps

* Update github-markdown

* Compile assets

* Switch to using Laravel Mix. Closes cachethq#2582

* Remove gulp dependency

* Fixes Date issue with incident dates being incorrect (as only loading out the date, not the time)

* Fix a spacing issue within text

* Fixes cachethq#2579

* Check if GLOB_BRACE is defined before using it. Fixes cachethq#2586

* Add comment as to why we define GLOB_BRACE as 0

* Prevent subscibing to internal components when not logged in

Fixes cachethq#2520

* Fixes incorrect timestamp on Scheduled Maintenances

Fixes cachethq#2578

* Add missing dev dependency

* Extend BrowserKitTesting TestCase class