use entypo namespace

[staaky]

Thanks for making this! Here's a couple suggestions to make things play nicer with Sass.

I ended up switching the .icon- prefix to .entypo- so the libary can be used alongside other libraries like font-awesome. I also extended your font definition to include .entypo so it ends up being:

.entypo, [class^="entypo-"], [class*=" entypo-"]

This allows easy switching between icon libraries in Sass, without having to define extra classes in the markup:

// entypo
.icon-user { @extend .entypo, .entypo-user }

// font-awesome
.icon-user { @extend .fa, .fa-user }