Decide what to do about '/'

One of our users correctly pointed out that we're disagreeing with the standard 
in our treatment of the '/' character. 

https://groups.google.com/forum/#!topic/google-gson/c77R5HgDk3o

This isn't a regression; As far as I can tell we've always had this behavior. 
In fact, android.util.JsonReader was changed to do it this way for consistency 
with GSON on this change: eb97c0ddc063176c26065fc6855188edf0c16e03