update linkcheck

Author: mark-i-m

.travis.yml

@@ -12,7 +12,7 @@ before_install:
 install:
 - source ~/.cargo/env || true
 - cargo install mdbook --version 0.4.0
-- cargo install mdbook-linkcheck --version 0.5.0
+- cargo install mdbook-linkcheck --version 0.7.0
 script:
 - git checkout -b ci
 - git rebase origin/master