Load RSA keys as pem format directly, and using openssl crate, backported from async branch

src/util.rs

@@ -219,6 +219,14 @@ pub fn read_file(path: &str) -> IOResult<Vec<u8>> {
     Ok(contents)
 }
 
+pub fn write_file(path: &str, content: &[u8]) -> Result<(), crate::error::Error> {
+    use std::io::Write;
+    let mut f = File::create(path)?;
+    f.write_all(content)?;
+    f.flush()?;
+    Ok(())
+}
+
 pub fn read_file_string(path: &str) -> IOResult<String> {
     let mut contents = String::new();