Add config for building and testing with Travis CI on each push

.travis.yml

@@ -0,0 +1,16 @@
+language: rust
+sudo: false
+
+cache:
+  - cargo
+
+rust:
+  - stable
+
+before_script:
+  - (test -x $HOME/.cargo/bin/cargo-install-update || cargo install cargo-update)
+  - (test -x $HOME/.cargo/bin/mdbook || cargo install --vers "^0.3" mdbook)
+  - cargo install-update -a
+
+script:
+  - mdbook build && mdbook test