split into lib and bin

* makes most pub things in src/ pub(crate) as not to expose things accidentally
  * only those things needed by src/bin/scryer-prolog.rs and tests/scryer.rs
    should be pub
* split src/main.rs into src/lib.rs and src/bin/scryer-prolog.rs
* add tests folder and run most of the files in src/tests with cargo test
  added bytes method to Stream in src/machine/streams.rs to check if stdout is as expected

tests/scryer.rs

@@ -0,0 +1,65 @@
+/// Loads the file and if some expected output is given checks that it matches
+fn test_file(file: &str, expected: Option<&[u8]>) {
+    use scryer_prolog::*;
+
+    let input = machine::Stream::from("");
+    let output = machine::Stream::from(String::new());
+
+    let mut wam = machine::Machine::new(input, output.clone());
+
+    wam.load_file(
+        file.into(),
+        machine::Stream::from(
+            std::fs::read_to_string(AsRef::<std::path::Path>::as_ref(file)).unwrap(),
+        ),
+    );
+
+    if let Some(expected) = expected {
+        let output = output.bytes().unwrap();
+        assert_eq!(output.as_slice(), expected);
+    }
+}
+
+#[test]
+fn builtins() {
+    test_file("src/tests/builtins.pl", Some(b""));
+}
+
+#[test]
+fn call_with_inference_limit() {
+    test_file("src/tests/call_with_inference_limit.pl", Some(b""));
+}
+
+#[test]
+fn facts() {
+    test_file("src/tests/facts.pl", Some(b""));
+}
+
+#[test]
+fn hello_world() {
+    test_file(
+        "src/tests/hello_world.pl",
+        Some("Hello World!\n".as_bytes()),
+    );
+}
+
+#[test]
+fn predicates() {
+    test_file("src/tests/predicates.pl", Some(b""));
+}
+
+#[test]
+fn rules() {
+    test_file("src/tests/rules.pl", Some(b""));
+}
+
+#[test]
+#[ignore] // ignored as this does not appear to terminate
+fn setup_call_cleanup() {
+    test_file("src/tests/setup_call_cleanup.pl", Some(b""));
+}
+
+#[test]
+fn clpz() {
+    test_file("src/tests/clpz/test_clpz.pl", Some(b""));
+}