Do not check changes in /doc, always build

.travis.yml

@@ -5,16 +5,6 @@ rust:
 - beta
 - stable
 cache: cargo
-before_install:
-- |
-  c=$(git diff $(git merge-base master $TRAVIS_COMMIT)..$TRAVIS_COMMIT --name-only | cut -d "/" -f 1 | uniq)
-  if [[ "$c" == "doc" ]]; then
-      echo "Only changes in DOC, exiting 0"
-      exit 0
-  else
-    echo "Changes in other directories than ./doc"
-    echo "continue build..."
-  fi
 before_script:
 - |
   pip install 'travis-cargo<0.2' --user &&