travis: add travis postback for rust-embedded-bot

Also update the versions of rust being tested.

Signed-off-by: Paul Osborne <osbpau@gmail.com>

Author: posborne

.travis.yml

@@ -1,9 +1,13 @@
 language: rust
+sudo: false
 rust:
   - 1.2.0
   - 1.3.0
   - 1.4.0
   - 1.5.0
+  - 1.6.0
+  - 1.7.0
+  - stable
   - beta
   - nightly
 env:
@@ -22,5 +26,5 @@ after_success: ! '[ $TRAVIS_BRANCH = master ] && [ $TRAVIS_PULL_REQUEST = false
   && ghp-import -n target/doc
   && git push -fq https://${GH_TOKEN}@github.com/${TRAVIS_REPO_SLUG}.git gh-pages'
 
-# Use Travis container-based system (much faster to start up)
-sudo: false
+notifications:
+  webhooks: http://rust-embedded-bot.herokuapp.com/travis