sync with upstream

Treat <input type="button"> as a clickable button

Also fixes a class of issues where all buttons were being sent
back as fields, causing undefined behavior on certain sites.

Merge pull request headzoo#62 from ethankent/master

Fix typo

Changelog update

Small change to docs

Added Browser.SetTransport() method

See headzoo#15

Updated the change log

Added Browser.body, Download() writes the body without modification

headzoo#13

Updated the change log

Updated the changelog