Improve spec for String#split with capture and limit
Improve spec for String#split with capture and limit

* use an example where the result with limit is different from the
  result without limit, and that also demonstrates that the limit
  is not applied separately to both split fields and captures
* improve wording of spec description

eregon/rubyspec,nobu/rubyspec,ruby/rubyspec,nobu/rubyspec,ruby/spec,eregon/rubyspec,sgarciac/spec,ruby/spec,eregon/rubyspec,sgarciac/spec,ruby/spec,nobu/rubyspec,sgarciac/spec,ruby/rubyspec