fix the rebase trick

Author: mark-i-m

.travis.yml

@@ -14,6 +14,8 @@ install:
 - cargo install mdbook --version 0.3.7
 - cargo install mdbook-linkcheck --version 0.5.0
 script:
+- git checkout -b ci
+- git rebase origin/master
 - git log --oneline | head -n 10
 - mdbook build
 notifications: