use bindings to eliminate fixed path search for node module

Author: Andy Dill

lib/spellchecker.js

@@ -1,5 +1,5 @@
 var path = require('path');
-var bindings = require('../build/Release/spellchecker.node');
+var bindings = require('bindings')('spellchecker.node');
 
 var Spellchecker = bindings.Spellchecker;
 

package.json

@@ -24,6 +24,7 @@
     "jasmine-focused": "1.x"
   },
   "dependencies": {
+    "bindings": "^1.2.1",
     "nan": "^2.0.0"
   }
 }