Release of std.io v0.3.0

[Steven Schveighoffer]

I have released a minor improvement to std.io [1], which adds support 
for opening the standard handles (stdin, stdout, stderr) [2].

In order to make this work, I also had to add a feature to IOs that 
allows you to temporarily use a file descriptor/handle [3].

As of now, it hasn't updated on code.dlang.org, but it should be soon.

With this, I'm going to focus next on making an iopipe/io layer that can 
replace write[f]ln and friends.

-Steve

[1] https://code.dlang.org/packages/io
[2] https://martinnowak.github.io/io/std/io/driver.html
[3] https://martinnowak.github.io/io/std/io/file/File.this.html