chore: remove tokio-trace, add "Related Projects" to README (v0.1) (#1223)

* chore: remove `tokio-trace`, add "Related Projects" to README (#1221)

The `tokio-trace` and `tokio-trace-core` crates have been renamed to
`tracing` and `tracing-core`, and moved to their own repository
(`tokio-rs/tracing`).

This branch removes `tokio-trace` and `tokio-trace-core` from the
`tokio` repository. In addition, I've added a "Related Projects" section
to the root README, which lists `tracing` (as well as  `mio`, and
`bytes`) as other libraries maintained by the Tokio project. I thought
that this would help folks looking for `tokio-trace` here find it in its
new home.

In addition, it changes `tokio` to depend on `tracing-core` rather than
`tokio-trace-core`.

Closes #1159

Signed-off-by: Eliza Weisman <[email protected]>

* Remove erroneous add of `tokio-macros`

* Some more tokio-trace remnants

* Remove tokio-trace remnants from Cirrus CI

* disable tracing-core feature by default

It can't build on Rust 1.26.0

Signed-off-by: Eliza Weisman <[email protected]>

* fix feature flagging

Signed-off-by: Eliza Weisman <[email protected]>

.cirrus.yml

@@ -32,8 +32,6 @@ task:
   test_script:
     - . $HOME/.cargo/env
     - cargo test --all
-    - (cd tokio-trace/test-log-support && cargo test)
-    - (cd tokio-trace/test_static_max_level_features && cargo test)
     - cargo doc --all
   i686_test_script:
     - . $HOME/.cargo/env