Lets use inline array instead passed array as param

I have already create the same changes for the capistrano/bundler gem.

Example of the problem:

```
set :bundle_roles, %w{web jobs}
```

For the current version it will raise exception on role_filter like:

```
undefined method `to_sym' for ["web", "jobs"]:Array
vendor/bundle/ruby/2.1.0/gems/capistrano-3.0.1/lib/capistrano/configuration/servers/role_filter.rb:25:in `each'
```

Example for this change: https://gist.github.com/oivoodoo/8342230