ci(travis): run shellcheck during lint job [skip ci]

* Automated using https://github.com/myii/ssf-formula/pull/106

pre-commit_semantic-release.sh

@@ -14,9 +14,9 @@ sed -i -e "s_^\(version:\).*_\1 ${1}_" FORMULA
 sudo -H pip install m2r
 
 # Copy and then convert the `.md` docs
-cp *.md docs/
-cd docs/
-m2r --overwrite *.md
+cp ./*.md docs/
+cd docs/ || exit
+m2r --overwrite ./*.md
 
 # Change excess `H1` headings to `H2` in converted `CHANGELOG.rst`
 sed -i -e '/^=.*$/s/=/-/g' CHANGELOG.rst