Merge #179: Fixed error message for too long hrp prefix

c0220d8 Run 'cargo +nightly fmt' on this. Options in rustfmt.toml apply only in nightly channel. (Dariusz Depta)
9309183 Removed unneeded test. (Dariusz Depta)
ef50d6d Fixed error message for too long hrp. (Dariusz Depta)

Pull request description:

  closes #178

ACKs for top commit:
  apoelstra:
    ACK c0220d8 though in future, please squash together commits which modify previous commits

Tree-SHA512: e876684ad0560c268af695500af0936dd8803598325e61647589c8f5469a8002bb7c18fc547a1a691803ab0d40b8b6e713ae22f1ff63ec56c38af38567f04d98

src/primitives/hrp.rs

@@ -393,7 +393,8 @@ impl fmt::Display for Error {
         use Error::*;
 
         match *self {
-            TooLong(len) => write!(f, "hrp is too long, found {} characters, must be <= 126", len),
+            TooLong(len) =>
+                write!(f, "hrp is too long, found {} characters, must be <= {}", len, MAX_HRP_LEN),
             Empty => write!(f, "hrp is empty, must have at least 1 character"),
             NonAsciiChar(c) => write!(f, "found non-ASCII character: {}", c),
             InvalidAsciiByte(b) => write!(f, "byte value is not valid US-ASCII: \'{:x}\'", b),