Fix confusing #[path] usage and re-exports in lib.rs

This has effectively the same behaviour now with fewer lines, less
confusion and fewer compiler warnings about unused code.

src/lib.rs

@@ -1,7 +1,5 @@
-#[path = "playlist.rs"]
 pub mod playlist;
 
-#[path = "parser.rs"]
 #[cfg(feature = "parser")]
 mod parser;
 

src/parser.rs

@@ -74,8 +74,6 @@
 //!
 //! ```
 
-pub mod playlist;
-
 use nom::branch::alt;
 use nom::bytes::complete::{is_a, is_not, tag, take, take_until, take_while1};
 use nom::character::complete::{