Refactored UInt and Derived Classes (#83)

Refactored UInt and Derived classes to be constructed from Buffers, and swapped out BN.js in favor of BigInt to reduce dependencies.

packages/ripple-binary-codec/src/serdes/binary-parser.ts

@@ -33,7 +33,7 @@ class BinaryParser {
    * @return The bytes
    */
   read(n: number): Buffer {
-    assert(n <= this.bytes.byteLength);
+    assert(n <= this.bytes.byteLength, n + " greater than " + this.bytes.byteLength);
 
     const slice = this.bytes.slice(0, n);
     this.skip(n);