CSS: Split into modules

Don't place pure styling on top-level files (those that don't begin with underscore).
Instead, import them as individual files.

src/styles/components/_base.sass

@@ -0,0 +1,32 @@
+body
+	height: 100%
+
+	+media-sm
+		width: 100%
+		max-width: 100%
+		min-width: auto
+
+	+media-xs
+		width: 100%
+		max-width: 100%
+		min-width: auto
+
+.container
+	+media-xs
+		max-width: 100%
+		min-width: auto
+		padding:
+			left: 0
+			right: 0
+
+	&.box
+		+container-box
+
+.container-page
+	background-color: white
+
+.page-content
+	position: relative
+	flex: 1
+	.container-box
+		+container-box