Int formatting working

+ Using num-bigint to support arbitrarily sized ints
+ Added formatting tests

src/byte_stream/mod.rs

@@ -3,7 +3,7 @@ pub enum ByteStreamError {
     OutOfRange,
 }
 
-const fn bit_mask(mask: u8) -> u8 {
+pub const fn bit_mask(mask: u8) -> u8 {
     match mask {
         0 => 0x00,
         1 => 0x01,