New versioning since v4.0.0

Since Angular provides often major versions that break compatibility of components, angular2gridster will provide also major versions adequate to major versions of angular. This kind of versioning will start with v4.0.0.

Moreover, version v4.0.0 will provide one breaking change. The module definition in versions v0.x and v1.x looks as follows:

@NgModule({
    imports: [
        ...
        GridsterModule
    ]
})
...

Since v4.0.0 looks as follows:

@NgModule({
    imports: [
        ...
        GridsterModule.forRoot()
    ]
})
...