Allow creation of a machine from string

src/ijvmreader.rs

@@ -20,6 +20,13 @@ impl IJVMReader {
             source: abc
         })
     }
+
+    pub fn new_from_string(source: String) -> IJVMReader {
+        IJVMReader {
+            pointer: 0,
+            source: source.into_bytes(),
+        }
+    }
 }
 
 impl BinReadable for IJVMReader {