Start reimplementing parser

Cargo.toml

@@ -11,3 +11,9 @@ keywords = ["logic"]
 categories = ["data-structures", "science"]
 license = "MIT"
 edition = "2018"
+
+[dependencies]
+nom = {version = "5.1", optional = true}
+
+[features]
+parse = ["nom"]

src/lib.rs

@@ -1,4 +1,6 @@
 mod ast;
 pub mod format;
+#[cfg(feature = "parse")]
+pub mod parse;
 
 pub use ast::*;