Prepare 0.17.4 release

[djc]

Fixes #541.

Changelog:

• Handle newline in msg and empty msg (#540, thanks to RDruon)
• Handle terminal line wrap to avoid new line (#533, thanks to RDruon)
• Resetting the elapsed time also resets ETA (#538, thanks to afontenot)
• Mention the prefix and message placeholders in the with_ docs (#529, thanks to lnicola)
• Allow rate-limiting TermLike targets (#526, thanks to akx)
• Fix docs for ProgressDrawTarget (#523, thanks to tillarnold)
• Change "OS X" to "macOS" (#519, thanks to atouchet)
• Fix MultiProgress alignment handling and migrate from structopt => clap (#516)
• Don't deadlock when double-adding ProgressBar (#515)
• Use instant::Instant when compiling to WASM (#514, thanks to azriel91)
• Update portable-atomic requirement from 0.3.15 to 1.0.0 (#512)
• inc() after work in examples (#522, thanks to tatref)