Modify regex_replace to return Iterator
Cleanup edit function

Use boxed iterators instead of Vecs. This should also reduce a few
memory allocations.
Use CRLF in response headers
Treat "" as a single-line document
Fix bug with empty line at the end

str.lines() makes a \n at the end of file optional, but also prevents
having an empty line at the end. This makes editing twinwiki painful.

Switch to plain .split('\n') instead.
Fix parsing urls with percent encoding
Add copyright and license headers
fix clippy warnings
Minor tweaks to main.rs
Implement `s` command
only add history entry if page changed
history: most recent first
Make "\n" default page content

This makes it easier to edit, as ifoo and afoo work.
only respond with help on missing front page
implement reverting old versions
add global footer with link to help
Add default front page
add tests and fix 'i' command