Add a utility read_to_string() function.

src/tools/utils.rs

@@ -0,0 +1,13 @@
+//! Utility functions.
+
+use std::path::Path;
+use std::fs::File;
+use std::io::{Result, Read};
+
+/// Read an entire file into a string.
+pub fn read_to_string<P: AsRef<Path>>(path: P) -> Result<String> {
+    let mut file = try!(File::open(path));
+    let mut buffer = String::new();
+    try!(file.read_to_string(&mut buffer));
+    Ok(buffer)
+}