Update underlying channel implementation

Changed

• Replace futures-channel with async-channel for the underlying channel implementation for pipes. This delivers slightly better performance and compile times. (#18, #19)

Race condition bugfix

Fixed

• Fix panic caused by race condition when writing while dropping reader. (#16)

Dependency trimming

Changed

• Remove the futures-util dependency, which is a bit heavier than desired, and we didn't really need it anyway.

AsyncBufRead and dependency fix

Added

• PipeReader now also implements AsyncBufRead.(#8)

Fixed

• Fix io feature of futures-util missing from dependencies, causing a compile error if the feature was not being implicitly enabled by some other dependency (like dev dependencies). (#10, #11) @ignatenkobrain

Dependency optimizations

Changed

• Do not require default features for futures-util since we do not use them. (#7) @jakobhellermann

Futures upgrade

Changed

• Upgraded from futures-preview to futures 0.3. This is a breaking change.

Bugfix for reading closed pipes

Fixed

• Fix a bug where reading from a pipe after already returning EOF would cause a panic. This was caused by Stream::poll_next used internally in the chunked implementation panicking after returning the final stream item, which it is allowed to do according to the current documentation. (#6)

Minor optimizations

Improvements

• Sluice now only depends on the futures sub-crates that it actually uses.
• Add a slight optimization to the chunked pipe writer that checks if the pipe is closed first before writing. Before the optimization, we were first copying the entire write buffer to the pipe, and then discovering that the pipe is closed and returning an error.

Implement Debug for reader and writer

Added

• Added Debug implementations for PipeReader and PipeWriter.

BrokenPipe error on writer drop

Fixed

• Fix an issue where dropping the writer while some data still remained in the pipe caused the reader to return a BrokenPipe error instead of allowing you to drain the bytes in the pipe until empty.