Fix an issue whereby colorization would output ANSI codes if a pager was
not configured.
The solution here is to stop guessing about the state of the user's
system at runtime, as well as the user's intention. The installer now
chooses an appropriate installer when generating configs, and no longer
bothers searching for pagers at runtime.
Fix an issue whereby the installer installed cheatsheets into the wrong
directory on Windows. This occurred because previously `path.Join` was
used where `path/filepath.Join` should have been used.
This matters, because the former always uses `/` as the path separator,
whereas the latter will use `/` or `\` as is appropriate for the
runtime environment.
This should resolve bullet point 4 in #665.
