Added support for CommonJS/browserify.

Author: clayzermk1

src/raven.js

@@ -4,7 +4,7 @@
 // If there is no JSON, we no-op the core features of Raven
 // since JSON is required to encode the payload
 var _Raven = window.Raven,
-    hasJSON = !!(window.JSON && window.JSON.stringify),
+    hasJSON = !!(typeof JSON === 'object' && JSON.stringify),
     lastCapturedException,
     lastEventId,
     globalServer,

template/_footer.js

@@ -1,9 +1,13 @@
 // Expose Raven to the world
-window.Raven = Raven;
-
-// AMD
 if (typeof define === 'function' && define.amd) {
+    // AMD
     define('raven', [], function() { return Raven; });
+} else if (typeof module === 'object') {
+    // CommonJS
+    module.exports = Raven;
+} else {
+    // Everything else
+    window.Raven = Raven;
 }
 
 })(window);