support for angular 5 - replace ngOutletContext with ngTemplateOutletContext

[jaa1982]

https://github.com/dmacfarlane/angular2-mentions/blob/b13b77bab4a7ac4edc10cf93c23b47c8e77f1b49/src/mention/mention-list.component.ts#L40

Angular v5 removes support for NgTemplateOutlet#ngOutletContext in favor of ngTemplateOutletContext , which now results in a compile time error if included. Per docs, this has actually been deprecated since Angular 4, but did not result in a compile time error

angular/angular@7522987

It looks like there is just one reference to ngOutletContext on the above line. If this could be replaced with ngTemplateOutletContext , we could support both Angular 4 & 5

[dmacfarlane]

Version 0.7.2 published to fix this. Thanks.