Updated nan version.
Updated nan version.

Updated nan to using the most recent npm version
rather than a git url, as all important changes have
been merged, and this removes the need for git to
be installed to `npm install` couchnode.

Change-Id: I4a3718892f49b3368af46b40c8ab2cd6dd183f42
Reviewed-on: http://review.couchbase.org/33205
Reviewed-by: Mark Nunberg <e7d42768707bf23038325b0b68d4b577e5f6064a@haskalah.org>
Tested-by: Brett Lawson <c8c4369773d7d7226e031f0c4af62e3f38a08510@gmail.com>

corbinu/couchnode,GannettDigital/couchnode,ConnectedHomes/couchnode,couchbase/couchnode,jess-sheneberger/couchnode,actano/couchnode,Bloutiouf/couchnode,Bloutiouf/couchnode,KenanSulayman/couchnode,kshmir/couchnode,brett19/couchnode,actano/couchnode,GannettDigital/couchnode,KenanSulayman/couchnode,ConnectedHomes/couchnode,brett19/couchnode,GannettDigital/couchnode,couchbase/couchnode,corbinu/couchnode,actano/couchnode,ConnectedHomes/couchnode,Bloutiouf/couchnode,jess-sheneberger/couchnode,couchbase/couchnode,ConnectedHomes/couchnode,jess-sheneberger/couchnode,couchbase/couchnode,KenanSulayman/couchnode,KenanSulayman/couchnode,corbinu/couchnode,jess-sheneberger/couchnode,brett19/couchnode,Bloutiouf/couchnode,kshmir/couchnode,kshmir/couchnode