--chain option for setting which network to go on.

Add contents function to util.

util/src/misc.rs

@@ -16,6 +16,7 @@
 
 //! Diff misc.
 
+use std::fs::File;
 use common::*;
 
 #[derive(Debug,Clone,PartialEq,Eq)]
@@ -53,3 +54,11 @@ pub enum Filth {
 	/// Data has been changed.
 	Dirty,
 }
+
+/// Read the whole contents of a file `name`.
+pub fn contents(name: &str) -> Result<Bytes, UtilError> {
+	let mut file = try!(File::open(name));
+    let mut ret: Vec<u8> = Vec::new();
+    try!(file.read_to_end(&mut ret));
+    Ok(ret)
+}