Fixed issue #479 where a crash would occur on swipe left

Also added a better spec runner from [this article](http://chen.do/blog/2013/06/03/running-individual-specs-with-rubymotion/) where you can do:

```sh-session
$ rake spec filter="partial or full name of spec"                   # To filter by spec name
$ rake spec files=foo_spec filter="partial or full name of spec"
$ rake spec hide_backtraces=yes                     # Hide backtraces
```

Ref #479.

```sh-session
240 specifications (463 requirements), 0 failures, 0 errors
```