fix exception in insight mocha browser tests

The Insight tests were actually broken and not running due to trying to access
the nonexistent process variable. The proper way to check for this is to see if
its type is undefined before trying to access it.

test/test.blockchain.Insight.js

@@ -60,7 +60,7 @@ describe('Insight model', function() {
   });
 
   // Tests for Node
-  if (process.version) {
+  if (typeof process !== 'undefined' && process.version) {
     it('should return array of unspent output', function(done) {
       var i = new Insight();