Have Travis run some sample builds

.travis.yml

@@ -8,4 +8,13 @@ rust:
   - nightly
   - beta
   - stable
-
+script:
+    - cargo build --verbose
+    - cargo test --verbose
+    - cargo run
+    - cargo run -- --long
+    - cargo run -- --long --grid
+    - cargo run -- --tree
+    - cargo run -- --tree --long
+    - cargo run -- --recurse
+    - cargo run -- --recurse --long --extended