Add comments to Hash methods
Merge pull request #2228 from suzukaze/add-comments-to-hash

Add comments to Hash methods
Add comment to Hash#each_pair. And change the line

Add comment about ISO.
Current place is misleading so change line No.
Merge pull request #2229 from yui-knk/add-comment-each_pair

Add comment to Hash#each_pair. And change the line
Fix document generator to remove trailing space in generated document.
Update generated document.
Merge pull request #2230 from take-cheeze/doc_update

Fix document generator to remove trailing space in generated document.