When saving/reading user-provided syntaxes or themes, `bat` will now maintain a
`metadata.yaml` file which includes information about the `bat` version which was
used to create the cached files. When loading cached files, we now print an error
if they have been created with an incompatible version
closes#882
When using `less` version 551 or newer, `bat` will now pass the `--mouse` argument, allowing
for (better) mouse scrolling support in some terminals.
closes#904