basic readme, cleanup token error

README.md

@@ -0,0 +1,17 @@
+# php-literal-parser
+
+parser for php literals.
+
+## Usage
+
+```rust
+use php_literal_parser::parse;
+use std::error::Error;
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let map = parse(r#"["foo" => true, "nested" => ['foo' => false]]"#)?;
+    assert_eq!(map["foo"], true);
+    assert_eq!(map["nested"]["foo"], false);
+    Ok(())
+}
+```