Comment typo fixes

Only comment changes.

Removed stray apostrophe from Util::Downloader.initialize() doc block. Corrected open => options for .download! description.
Add missing Vagrantfile docs
Merge pull request #2122 from psi/docs-fixes

website/docs: add missing Vagrantfile docs
Merge pull request #2120 from beporter/comment-typo-fixes

core: comment typo fixes