All uses of `unsafe` are now thoroughly documented with arguments and
informal proofs of correctness as well as conditions that must hold for
these arguments to pass.
This commit also reduces the number of `unsafe` uses by 7, bringing the
count to ~10 non-test uses of `unsafe`.
The directory structure has changed to better isolate crates serving
core and contrib. The new directory structure is:
contrib/
lib/ - the contrib library
core/
lib/ - the core Rocket library
codegen/ - the "compile extension" codegen library
codegen_next/ - the new proc-macro library
examples/ - unchanged
scripts/ - unchanged
site/ - unchanged
This commit also removes the following files:
appveyor.yml - AppVeyor (Rust on Windows) is far too spotty for use
rustfmt.toml - rustfmt is, unfortunately, not mature enough for use
Finally, all example Cargo crates were marked with 'publish = false'.
