Add lib/btoa.js for node.js btoa.

Author: chrisdickinson

lib/btoa.js

@@ -0,0 +1,4 @@
+var Buffer = require('buffer').Buffer
+module.exports = function(str) {
+  return (new Buffer(str, 'utf8')).toString('base64')
+}

package.json

@@ -8,6 +8,7 @@
         "test" : "test"
     },
     "dependencies" : {
+        "underscore":"1.X.X"
     },
     "devDependencies" : {
         "tracejs" : "0.X.X"