Format hex color code to lowercase

Format hex color code to lowercase #41.

and fixed some bugs.

• Fix Sass @if/@else formatting #54
• Don't add spaces to data-urls, fixes #53
• Fixes to Sass function and math formatting, fixes #52
• Format declarations for AtRules #49
• Don't add extra spaces to @include parameters #48
• Fix missing new lines for Sass functions #47
• Fix @charset formatting #46
• Specify indentataion size and style from .editorconfig #45

Thanks for @kristerkari :)