customdocstyle.html: Only the unmarked stability level is hidden
tests: Fix warnings
Add .map_unboxed for now
Add ZipLongest adaptor by Simon Sapin, method is .zip_longest()

ZipLongest originally written by SimonSapin,
and dedicated to itertools https://github.com/rust-lang/rust/pull/19283
Bump version to 0.0.5 for ZipLongest
Merge branch 'master' into gh-pages
Update docs