Merge pull request #498 from ovatsus/master

Add AppVeyor CI
Merge pull request #499 from ovatsus/master

Fix Japanese docs
Update README.md
Update README.md
Update ja/library/Http.fsx following changes of the original document.
Merge pull request #502 from yukitos/master

Update ja/library/Http.fsx following changes of the original document.
Release Beta 3