Make tests run cleanly

Little tweaks, but...

Before:

```
$ bundle exec rake test
Forth ".fth" is already defined in samples/. Remove from languages.yml.

*** Mocha deprecation warning: Change `require 'mocha'` to `require 'mocha/setup'`.

Run options: 

# Running tests:

.....................................................................................

Finished tests in 6.823390s, 12.4572 tests/s, 368.5851 assertions/s.

85 tests, 2515 assertions, 0 failures, 0 errors, 0 skips
```

After:

```
$ bundle exec rake test
Run options: 

# Running tests:

.....................................................................................

Finished tests in 6.983742s, 12.1711 tests/s, 360.1221 assertions/s.

85 tests, 2515 assertions, 0 failures, 0 errors, 0 skips
```