added benchmarks and few optimisations for rlp encoding

src/bytes.rs

@@ -60,6 +60,7 @@ impl ToBytes for u64 {
     fn to_bytes(&self) -> Vec<u8> {
         let mut res= vec![];
         let count = self.to_bytes_len();
+        res.reserve(count);
         for i in 0..count {
             let j = count - 1 - i;
             res.push((*self >> (j * 8)) as u8);
@@ -89,6 +90,7 @@ macro_rules! impl_uint_to_bytes {
             fn to_bytes(&self) -> Vec<u8> { 
                 let mut res= vec![];
                 let count = self.to_bytes_len();
+                res.reserve(count);
                 for i in 0..count {
                     let j = count - 1 - i;
                     res.push(self.byte(j));

src/uint.rs

@@ -233,7 +233,6 @@ macro_rules! construct_uint {
             type Err = FromHexError;
 
             fn from_str(value: &str) -> Result<$name, Self::Err> {
-                println!("{}", value);
                 let bytes: &[u8] = &try!(value.from_hex());
                 Ok(From::from(bytes))
             }