Add function for capitalizing strings

[femnad]

Hello,

This PR adds a capitalize function (name inspired by the Python string method) for converting a string to sentence case; first letter upper case, rest lower case.

I have a use case where a function like this would be useful and it's a small enough change so I'm creating this PR without a discussion issue but it's not a big loss if it doesn't get merged.

Thanks!

[casey]

Maybe something like this:

Suggested change

	let mut chars = s.chars();
	match chars.next() {
	None => Ok(String::new()),
	Some(c) => Ok(c.to_uppercase().collect::<String>() +
	&chars.as_str().to_lowercase()),
	}
	Ok(s.chars().enumerate().flat_map(|(i, c)| if i == 0 { c.upper_case() } else { c.lower_case() }).collect())

[femnad]

So much more elegant! Applied with rustfmt and some modifications.

[casey]

Good feature, and thanks for also adding a test! Very minor comment suggesting a slightly tweaked implementation.

[casey]

Also, could you add a note, like this to the function documentation: <sup>master</sup>. This is to indicate that the function is on master and not in a released version of just yet. I'll change it to the version it winds up being released in.

[femnad]

Added master designation to the function documentation:

[casey]

Merged! Thank you for the PR!