Change `timeField` to use `type="time"`

Followup to #874. Not to be merged until the next major release.

* `timeField` now uses `type="time"`
* Removes deprecation from `timeField`
* Mildly discourages using `timeFieldTypeText` in favor of `timeField` or `timeFieldTypeTime`

This approach is based on the description in https://github.com/yesodweb/yesod/pull/874#issuecomment-64408097. An alternate approach would be to deprecate `timeFieldTypeTime` and/or `timeFieldTypeText`, but this approach maximizes backwards compatibility.