retain_mut 0.1.1

Provide retain_mut method that has the same functionality as retain but gives mutable borrow to the predicate.
Documentation
Build #225672 2020-02-29T00:14:45.171194+00:00
# rustc version
rustc 1.43.0-nightly (6d69caba1 2020-02-27)
# docs.rs version
docsrs 0.6.0 (7de24ca 2020-02-23)

# build log
[INFO] running `"docker" "create" "-v" "/home/cratesfyi/workspace/builds/retain_mut-0.1.1/target:/opt/rustwide/target:rw,Z" "-v" "/home/cratesfyi/workspace/builds/retain_mut-0.1.1/source:/opt/rustwide/workdir:ro,Z" "-v" "/home/cratesfyi/workspace/cargo-home:/opt/rustwide/cargo-home:ro,Z" "-v" "/home/cratesfyi/workspace/rustup-home:/opt/rustwide/rustup-home:ro,Z" "-e" "SOURCE_DIR=/opt/rustwide/workdir" "-e" "MAP_USER_ID=1001" "-e" "CARGO_TARGET_DIR=/opt/rustwide/target" "-e" "RUSTFLAGS=" "-e" "RUSTDOCFLAGS=-Z unstable-options --resource-suffix -20200227-1.43.0-nightly-6d69caba1 --static-root-path /" "-e" "CARGO_HOME=/opt/rustwide/cargo-home" "-e" "RUSTUP_HOME=/opt/rustwide/rustup-home" "-w" "/opt/rustwide/workdir" "-m" "3221225472" "--network" "none" "rustops/crates-build-env" "/opt/rustwide/cargo-home/bin/cargo" "+nightly" "doc" "--lib" "--no-deps"`
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] [stdout] 95f88fc78dde479d7c79699fd4fed47b4e00ef49c68338987b8408e1545506f1
[INFO] running `"docker" "start" "-a" "95f88fc78dde479d7c79699fd4fed47b4e00ef49c68338987b8408e1545506f1"`
[INFO] [stderr]  Documenting retain_mut v0.1.1 (/opt/rustwide/workdir)
[INFO] [stderr]     Finished dev [unoptimized + debuginfo] target(s) in 0.95s
[INFO] running `"docker" "inspect" "95f88fc78dde479d7c79699fd4fed47b4e00ef49c68338987b8408e1545506f1"`
[INFO] running `"docker" "rm" "-f" "95f88fc78dde479d7c79699fd4fed47b4e00ef49c68338987b8408e1545506f1"`
[INFO] [stdout] 95f88fc78dde479d7c79699fd4fed47b4e00ef49c68338987b8408e1545506f1