Default gets the data as argument (#273)

* Default gets the data as argument

* Trailing space

Author: Guillaume Chau

Diff for: lib/ask.js

@@ -36,11 +36,19 @@ function prompt (data, key, prompt, done) {
   if (prompt.when && !evaluate(prompt.when, data)) {
     return done()
   }
+
+  var promptDefault = prompt.default
+  if (typeof prompt.default === 'function') {
+    promptDefault = function () {
+      return prompt.default.bind(this)(data)
+    }
+  }
+
   inquirer.prompt([{
     type: promptMapping[prompt.type] || prompt.type,
     name: key,
     message: prompt.message || prompt.label || key,
-    default: prompt.default,
+    default: promptDefault,
     choices: prompt.choices || [],
     validate: prompt.validate || function () { return true }
   }], function (answers) {