Address performance of try/catch in isJSONObject checks

I'm using the CouchBase Java Client and when performing large amounts of set's, the net.spy.memcached.util.StringUtils.isJsonObject() shows up a lot in my profiler as a performance bottleneck due to the overhead of catching exceptions related to attempting to cast strings to an Integer.

Use a different method of determining whether the incoming string is numeric that doesn't involve throwing and catching errors.

There are a couple different tickets in existence that suggest this entire method has serious issues and should be scrapped, but I'm unclear on the official response to that since one of the tickets is closed as a duplicate and the other is closed but seems completely unrelated.
http://www.couchbase.com/issues/browse/JCBC-48
http://www.couchbase.com/issues/browse/JCBC-41