Breaking 0.2 changes plan

[svartalf]

Since this crate is not abandoned anymore (yay!), it is time to make it a bit more modern and plan changes for the next 0.2 version.

• Determine minimal supported Rust version — (set to 1.19.0)
• Gather list of the supported OSes
• Add CI builds (how to test Redox and various *nix'es?) — Linux, macOS and Windows are enabled already
• Deprecate the get_hostname function
• Add get() -> io::Result<OsString> function
• Add set<T>(hostname: T) -> io::Result<()> where T: Into<OsStr> function (determine what exactly T should be)
• Replace winutil dependency with the winapi crate
• Use gethostname from the libc crate instead of bundled version
• Add keywords, categories and badges seasoning to the Cargo manifest
• Add more documentation and examples
• Review API guidelines and make the public API great
• Address the Avoidable, potential unsafety #6 issue

[svartalf]

There is a linker bug with 1.13.0 build for Windows, happens because of rust-lang/rust#38584
As bumping to 1.19.0 seems to be unreasonable, CI should be fixed instead with any workaround provided.

Temporary bumped to 1.19.0, it can be addressed later.

[svartalf]

How does get works for other languages/libraries:

	Python	Golang	NodeJS (via libuv)
*nix	gethostname		gethostname
Windows	GetComputerNameExW(ComputerNamePhysicalDnsHostname)	GetComputerNameExW(ComputerNamePhysicalDnsHostname)	gethostname
AIX		uname
darwin		sysctl("kern.hostname")
DragonFly/FreeBSD		sysctl("kern.hostname")
NetBSD		sysctl("kern.hostname")
OpenBSD		sysctl("kern.hostname")
Linux		uname + /proc/sys/kernel/hostname
Android		uname
Solaris		gethostname