New exception with Sneakers::Configuration

```
NoMethodError: undefined method `delete' for #<Sneakers::Configuration:0x007fddaf664da8>
/Users/arion/.rvm/gems/ruby-1.9.3-p545/bundler/gems/sneakers-5aa21aa50074/lib/sneakers/runner.rb:58:in `block in reload_config!'
/Users/arion/.rvm/gems/ruby-1.9.3-p545/bundler/gems/sneakers-5aa21aa50074/lib/sneakers/runner.rb:57:in `each'
/Users/arion/.rvm/gems/ruby-1.9.3-p545/bundler/gems/sneakers-5aa21aa50074/lib/sneakers/runner.rb:57:in `reload_config!'
/Users/arion/.rvm/gems/ruby-1.9.3-p545/bundler/gems/sneakers-5aa21aa50074/lib/sneakers/runner.rb:11:in `block in run'
/Users/arion/.rvm/gems/ruby-1.9.3-p545/gems/serverengine-1.5.9/lib/serverengine/config_loader.rb:39:in `call'
/Users/arion/.rvm/gems/ruby-1.9.3-p545/gems/serverengine-1.5.9/lib/serverengine/config_loader.rb:39:in `reload_config'
/Users/arion/.rvm/gems/ruby-1.9.3-p545/gems/serverengine-1.5.9/lib/serverengine/config_loader.rb:32:in `initialize'
/Users/arion/.rvm/gems/ruby-1.9.3-p545/gems/serverengine-1.5.9/lib/serverengine/daemon.rb:29:in `initialize'
/Users/arion/.rvm/gems/ruby-1.9.3-p545/gems/serverengine-1.5.9/lib/serverengine.rb:50:in `new'
/Users/arion/.rvm/gems/ruby-1.9.3-p545/gems/serverengine-1.5.9/lib/serverengine.rb:50:in `create'
/Users/arion/.rvm/gems/ruby-1.9.3-p545/bundler/gems/sneakers-5aa21aa50074/lib/sneakers/runner.rb:11:in `run'
/Users/arion/.rvm/gems/ruby-1.9.3-p545/bundler/gems/sneakers-5aa21aa50074/lib/sneakers/tasks.rb:32:in `block (2 levels) in <top (required)>'
/Users/arion/.rvm/gems/ruby-1.9.3-p545/bin/ruby_noexec_wrapper:14:in `eval'
/Users/arion/.rvm/gems/ruby-1.9.3-p545/bin/ruby_noexec_wrapper:14:in `<main>'
```
Merge pull request #62 from arion/patch-1

New exception with Sneakers::Configuration