refactor to a library, add integration tests

src/lib.rs

@@ -0,0 +1,18 @@
+#![recursion_limit = "1024"]
+
+extern crate chrono;
+extern crate uuid;
+#[macro_use]
+extern crate error_chain;
+
+mod tdb2;
+mod task;
+mod errors;
+
+use std::io::BufRead;
+pub use task::*;
+pub use errors::*;
+
+pub fn parse(filename: &str, reader: impl BufRead) -> Result<Vec<Task>> {
+    Ok(tdb2::parse(filename, reader)?)
+}