Fix type for uri and env options

Trollop doesn't recognize the type 'Array' as a valid option type which produced the following error:

    $ marathon start
    /Users/russell/.rvm/gems/ruby-1.9.3-p327/gems/trollop-2.0/lib/trollop.rb:145:in `opt': unsupported argument type
            'Class' (ArgumentError)
            from /Users/russell/.rvm/gems/ruby-1.9.3-p327/gems/marathon_client-0.0.7/bin/marathon:39:in `block in <top (required)>'
            from /Users/russell/.rvm/gems/ruby-1.9.3-p327/gems/trollop-2.0/lib/trollop.rb:82:in `call'
            from /Users/russell/.rvm/gems/ruby-1.9.3-p327/gems/trollop-2.0/lib/trollop.rb:82:in `initialize'
            from /Users/russell/.rvm/gems/ruby-1.9.3-p327/gems/trollop-2.0/lib/trollop.rb:709:in `new'
            from /Users/russell/.rvm/gems/ruby-1.9.3-p327/gems/trollop-2.0/lib/trollop.rb:709:in `options'
            from /Users/russell/.rvm/gems/ruby-1.9.3-p327/gems/marathon_client-0.0.7/bin/marathon:33:in `<top (required)>'
            from /Users/russell/.rvm/gems/ruby-1.9.3-p327/bin/marathon:19:in `load'
            from /Users/russell/.rvm/gems/ruby-1.9.3-p327/bin/marathon:19:in `<main>'
            from /Users/russell/.rvm/gems/ruby-1.9.3-p327/bin/ruby_noexec_wrapper:14:in `eval'
            from /Users/russell/.rvm/gems/ruby-1.9.3-p327/bin/ruby_noexec_wrapper:14:in `<main>'

Changing the type to :strings fixes the issue.