ReadOnlyCollection type conflicts with VRTK #64

Looks like our inclusion of the ReadOnlyCollectionInterfaces nuget (to get System.Collections.Generic.ReadOnlyCollection<T> with the correct inheritance tree that satisfies Octokit's needs) is clashing with other plugins' use of the old System.Collections.ObjectModel.ReadOnlyCollection<T> type.

The easy fix is for VRTK to disambiguate the type by specifying the namespace to it. However, we are adding new types to the .net namespace that scripts aren't expecting, so this breakage is likely to happen to other scripts as well. We should probably be nice citizens and not add types to the System namespaces to avoid random clashes like this.

We might have to remove or change ReadOnlyCollection<T> usage from Octokit so we don't have to depend on the new type, or we can rename the namespace so it's not sitting in the System.* namespace.