Add cargo fmt to travis build config

Author: Atul9

.travis.yml

@@ -3,6 +3,13 @@ rust:
   - stable
   - nightly
 script:
+  - |
+    if [[ $TRAVIS_RUST_VERSION == *stable* ]]
+    then
+      rustup component add rustfmt
+      cargo fmt --version
+      cargo fmt -- --check || (echo "Please reformat your code with 'cargo fmt' (version $(cargo fmt --version))"; false)
+    fi
   - cargo test
   - |
     [ $TRAVIS_RUST_VERSION != nightly ] ||