Fix Ruby warnings.

* utils.rb:24: warning: assigned but unused variable - parts
* gateway.rb:115: warning: character class has duplicated range: /\shref="\/wiki\/([\w\(\)_\-\.%\d:,]*)"/
* gateway.rb:346: warning: assigned but unused variable - in_progress
* gateway.rb:508: warning: assigned but unused variable - dummy
* gateway.rb:515: warning: assigned but unused variable - imgs
* gateway.rb:537: warning: assigned but unused variable - dummy
* gateway.rb:609: warning: assigned but unused variable - dummy
* gateway.rb:697: warning: assigned but unused variable - dummy
* gateway.rb:730: warning: assigned but unused variable - dummy
* gateway.rb:755: warning: assigned but unused variable - dummy
* gateway.rb:778: warning: assigned but unused variable - dummy
* gateway.rb:787: warning: assigned but unused variable - dummy
* gateway.rb:795: warning: assigned but unused variable - dummy
* gateway.rb:808: warning: assigned but unused variable - dummy
* gateway.rb:825: warning: assigned but unused variable - dummy
* gateway.rb:843: warning: assigned but unused variable - dummy
* gateway.rb:917: warning: mismatched indentations at 'end' with 'case' at 901
* gateway.rb:960: warning: shadowing outer local variable - e
* gateway.rb:949: warning: assigned but unused variable - e

Ruby versions checked: 2.1.2p95 and 1.9.3p484.