JSCBC-50: Updated key option parser to accept Numeric types.

v8 blurs the lines between String and Numeric types when they are
interchangable.  Updated the key option parser such that it will respect
this and preform an implicit conversion from a number to a string.

Change-Id: I915152c52175165083b7e7d40cac1bf5bd665342
Reviewed-on: http://review.couchbase.org/28836
Tested-by: Brett Lawson <brett19@gmail.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>