documentation auto update

.travis.yml

@@ -1 +1,12 @@
 language: rust
+after_success: |
+  [ $TRAVIS_BRANCH = master ] &&
+  [ $TRAVIS_PULL_REQUEST = false ] &&
+  cargo doc &&
+  echo "<meta http-equiv=refresh content=0;url=`echo $TRAVIS_REPO_SLUG | cut -d '/' -f 2`/index.html>" > target/doc/index.html &&
+  sudo pip install ghp-import &&
+  ghp-import -n target/doc &&
+  git push -fq https://${GH_TOKEN}@github.com/${TRAVIS_REPO_SLUG}.git gh-pages
+env:
+  global:
+  - secure: SZSxNqg9wiGx8EnJhifJ2kb/aCRcLim9TzTQyfurPqd8qVGkDOeVjTtbs+VTxLVXYtMJAz+YYnrQDwsu8kc/uYpQajU+gRMqNGEP5gNj3Ha5iNGDasAS6piIHQSMROayZ+D9g22nlGnjk8t9eZtLHC/Z8IWMCnjcIHvqMFY6cgI=