Allow for other units

Provide values for px, pc, em, ex and utilize switch for divisor determination.

Author: brettz9

jspdf.js

@@ -788,16 +788,33 @@ var jsPDF = (function(global) {
 			// @TODO: Add different output options
 		});
 
-		if (unit === 'pt') {
-			k = 1;
-		} else if (unit === 'mm') {
-			k = 72 / 25.4;
-		} else if (unit === 'cm') {
-			k = 72 / 2.54;
-		} else if (unit === 'in') {
-			k = 72;
-		} else {
-			throw('Invalid unit: ' + unit);
+		switch (unit) {
+			case 'pt':
+				k = 1;
+				break;
+			case 'mm':
+				k = 72 / 25.4;
+				break;
+			case 'cm':
+				k = 72 / 2.54;
+				break;
+			case 'in':
+				k = 72;
+				break;
+			case 'px':
+				k = 96 / 72;
+				break;
+			case 'pc':
+				k = 12;
+				break;
+			case 'em':
+				k = 12;
+				break;
+			case 'ex':
+				k = 6;
+				break;
+			default:
+				throw ('Invalid unit: ' + unit);
 		}
 
 		// Dimensions are stored as user units and converted to points on output