Merge pull request #524 from octatone/isFinite

New Feature: _.isFinite to compliment _.isNumber and _.isNaN

underscore.js

@@ -824,6 +824,11 @@
     return toString.call(obj) == '[object Number]';
   };
 
+  // Is a givin number finite?
+  _.isFinite = function(obj) {
+    return _.isNumber(obj) && isFinite(obj);
+  };
+
   // Is the given value `NaN`?
   _.isNaN = function(obj) {
     // `NaN` is the only value for which `===` is not reflexive.