Merge pull request #72 from simon-jentzsch/master

added Error when dealing with negativ integers for

src/index.ts

@@ -207,6 +207,9 @@ function stripHexPrefix(str: string): string {
 
 /** Transform an integer into its hexadecimal value */
 function intToHex(integer: number): string {
+  if (integer < 0) {
+    throw new Error('Invalid integer as argument, must be unsigned!')
+  }
   const hex = integer.toString(16)
   return hex.length % 2 ? `0${hex}` : hex
 }