HermitVersion: Added new fn

[jounathaen]

The sole purpose of this function is to remove the four extra lines of code when instantiating this struct.

[mkroening]

I've not done it this way deliberately, because without inline hints, I find

HermitVersion::new(0, 1, 2)

less readable than

HermitVersion {
    major: 0,
    minor: 1,
    patch: 2,
}

Compare to the main usage of the semver crate (and tests).

Adding this is fine with me. This is similar to semver::Version::new, though that method functions to avoid spelling out pre and build.

I am unsure if changing the tests is the right call, but you can do as you wish. :)

[jounathaen]

Then let's merge it. It isn't a big thing but doesn't hurt.