Add printf1 function

[gustaphe]

Implements printf1([io],fmt,x) function to work as a drop-in replacement for @print.

A bit of a hack: simply calls print(io,sprintf1(fmt, x)), so offers no performance benefit over sprintf1, but is QOL. My original idea was to rewrite sprintf1 into printf1, and make sprintf1 work via an IOBuffer, but because sprintf1 does several replacements and similar operations that require strings I decided to not touch it for now.

Temporary fix for #91

[kescobo]

This package is no longer maintained (see #111). Please consider using Format.jl instead, and if this feature is unavailable / still desired, open an issue or PR there.