Fix the gemspec loading order of dependencies

Was getting the following type of errors when running bundle:

```
There was a LoadError while loading chronic.gemspec: 
cannot load such file -- numerizer from
  /opt/rubies/2.1.1/lib/ruby/gems/2.1.0/bundler/gems/chronic-cd739fdf316d/chronic.gemspec:2:in `<main>'

Does it try to require a relative path? That's been removed in Ruby 1.9.
```

This removes the need for the entire library to be loaded when parsing the gemspec