NCBC-381: (revision) Ensure that Nuget installs Newtonsoft.JSON <= 5.0.8

Original patch restricted version to 4.5.11, this restricts version to less or equal
to 5.0.8. Version 6.X breaks GetJson and will be resolved in the 1.3.3 release of the client

Change-Id: Iafbc853892fbb75bd6fb2fe9ab987753f7822828
Reviewed-on: http://review.couchbase.org/33301
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>