Update documentation page (zh_cn)

Add editors and IDEs section.
Remove trailing whitespace (zh_cn)
Revert link references on downloads page (it)
Rename to-ruby-from-c-and-c- to to-ruby-from-c-and-cpp
Fix/improve rewrite rules
Fix links to to-ruby-from-c-and-cpp
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Merge pull request #254 from gozali/master

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Merge remote-tracking branch 'upstream/master'