Missing title leads to tests always passing (#1)

* Missing title leads to tests always passing

testChanged('a', 'b') => 
createTest(title='a', input='b', expected=undefined)

before:
title='a'
input='b'
expected='b'

after:
title='a'
input='a'
expected='b'

* Fixing order

index.js

@@ -27,6 +27,7 @@ function testPlugin(jscodeshift, test, plugin) {
     // If there is no title, use input as title
     if (title && input && !expected) {
       expected = input;
+      input = title;
     }
     test(title, function (t) {
       t.is(runPlugin(plugin, input), expected);