Fixed tag casing
Added quick F# script to re-generate tag files based on posts

Deletes anything from /tags/ that isn't referenced by posts, and adds
new tags for anything in /_posts/.
Re-created tags using F# script

Removed unused (or incorrectly named) files, and added new (or correctly
named) files.
Moved tags to include, so we can manually sort alphabetically

Although site.pages is alphabetical locally, it's not on GitHub :-/ So
the F# script that mantains the tags folder can also maintain
_includes/tags.htm now!
Write sorted tags include when updating tags via F# file
Updated tags

Ran F# script, which now dumps a sorted list of tags into the include
used in the nav.