Use I/O traits and types from 'tokio-io' as much as possible.
A few adapters only exist in futures-io-preview and use
futures-tokio-compat as a bridge for now.
The new 'FromData' trait allows an implementor to instruct the caller to
maintain state on its stack and later pass a borrow for processing.
Among other things, it greatly simplifies the 'Form' type, removing a
use of unsafe, and allows references in deserialized data guards.
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'.