Fix load path and requires. Fix a test.

Hi @elcuervo! Long time no see! :smile:

First of all, **thank you for this gem!**

I had a little issue when I cloned it and tried to run the test suite:

```bash
~/dev/github/cuba-sugar (master) ❯ bundle exec rake


LoadError: cannot load such file -- test_helper


```

Of course this works without bundler (ie. using gs+dep), but since you have a `Gemfile`, it would be nice to make it work. 

Once I fixed this and run the test suite, this happened:

```bash
~/dev/github/cuba-sugar (patch-1) ❯ bundle exec rake
.......

Cutest::AssertionFailed: ["  alpha\nbeta\ngamma\n"] != ["  alpha\nbeta\ngamma\n\n"]

- assert_equal body, ["  alpha\nbeta\ngamma\n\n"] test/content_for.rb +23

```

and fixed the test.

What do you think?