Use node::MakeCallback

These wrappers around ->Call are supposed to be used as they allow
proper handling of domains and nextTick. They also handle the TryCatch
stuff as well.

Change-Id: I5d1357801a07003dd1a40f986f52e1191d560947
Add benchmark for 'node-couchbase'

Change-Id: If9759c8863a8da4d1963198388dd0f12d5dee527
Beef up benchmark code

Change-Id: I25c0099f4c3ba7a00d5d2b84ec75b1cadd9404a4