Merge pull request #124 from u0u0/master

manually merge pull 122
update contribute guide
update contribute guide
Merge pull request #125 from darkdukey/master

Some clean up for the contribute guide
Update en.md

Adds more editors
Update en.md
Add 5 Chinese tutorials.
modify original links.
Merge pull request #126 from Ivenyang/master

add 5 tutorials.
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Merge pull request #127 from lorrylockie/patch-1

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fixed #4049, Update document of “How to use httpclient” to Cocos2d-x 3.0