Replace varint assert with exception (#146)

src/datatypes/utils.js

@@ -1,5 +1,3 @@
-const assert = require('assert')
-
 const { getCount, sendCount, calcCount, PartialReadError } = require('../utils')
 
 module.exports = {
@@ -77,7 +75,7 @@ function readVarInt (buffer, offset) {
       }
     }
     shift += 7 // we only have 7 bits, MSB being the return-trigger
-    assert.ok(shift < 64, 'varint is too big') // Make sure our shift don't overflow.
+    if (shift > 64) throw new PartialReadError(`varint is too big: ${shift}`) // Make sure our shift don't overflow.
   }
 }