improve folder structure

[luwes]

Makes life easier when using JS task runners. I guess this is more a matter of taste but I think this folder structure is handier. When you are building your project it seems having your fonts and builded stylesheets in a separate folder seems like a more generally used way.

[volodchenkov]

I think you can add fonts directory to main section of bower.json, because fonts files do not copy to build directory while build process. https://github.com/Swiip/generator-gulp-angular/issues/316