* use a trailing slash when possible
* use https when possible
* remove a few redirected links
* consistently use `https://popper.js.org/`
* fix `iconUrl` in nuget files
* change Jekyll Windows guide to the official one
I suggest that there's no longer a need to include the section on workaround for the IE10 bug on Windows Phone 8. Not only was this bug patched in a later release of Windows Phone 8 (which shipped in 2013), but Windows Phone 8's support ended a long time ago - even its successor Windows Phone 8.1 is no longer supported by Microsoft. The potential audience affected by this bug is likely microscopic so I suggest it can be safely removed.
I suggest the workaround JS (http://getbootstrap.com/assets/js/ie10-viewport-bug-workaround.js) can also be safely removed from the docs and examples but I haven't done that in this PR.
