Introduced ability to open csv documents.

tests/commands_test.rs

@@ -12,6 +12,15 @@ fn lines() {
     assert_eq!(output, "rustyline");
 }
 
+#[test]
+fn open_csv() {
+    nu!(output,
+        cwd("tests/fixtures/formats"),
+        "open caco3_plastics.csv | get root | first 1 | get origin | echo $it");
+
+    assert_eq!(output, "SPAIN");
+}
+
 #[test]
 fn open_toml() {
     nu!(output,