add half-width and quarter-width classes for images (#134)

Author: TatsatJha

assets/sass/_custom.sass

@@ -102,8 +102,18 @@ div.subscribe
 			margin-top: 0.25rem //this margin-top of 4px is necessary to align the icon with the text
 
 .half-width
-	max-width: 500px
+	max-width: 50%
+	float: left
+	margin-right: 2rem
+	display: block
 	height:auto
+.quarter-width
+	max-width: 25%
+	float: left
+	margin-right: 2rem
+	display: block
+	height:auto
+
 
 // font used in new dhtech logo; used in RSK post about creating logo
 @font-face