A peekable lexer

Use the chars() iterator on &str, with the Peekable wrapper on Iterators, to iterate the input, rather than needing to hold the whole input and do iteration by indexes.

lexer/src/main.rs

@@ -0,0 +1,14 @@
+/* lexer/src/main.rs
+ * Eryn Wells <eryn@erynwells.me>
+ */
+
+extern crate sibillexer;
+
+use sibillexer::Lexer;
+
+fn main() {
+    let lexer = Lexer::new("(ab (cd) ef)".chars());
+    for tok in lexer {
+        println!("found {:?}", tok.unwrap());
+    }
+}