Add inverted variables option (#110)

Abner Campanha

12.42.2018 720f7518a6de1ecf37e12bd3153817ba2e245152

 assets/scss/_variables.scss

@@ -9,3 +9,10 @@
$alt-bg-color: #E0E0E0 !default;
$alt-fg-color: #000 !default;
$link-color: #1565c0 !default;

// Colors inverted
$bg-color-inverted: #212121 !default;
$fg-color-inverted: #fafafa !default;
$alt-bg-color-inverted: #424242 !default;
$alt-fg-color-inverted: #fafafa !default;
$link-color-inverted: #f44336 !default;