Merge pull request #428 from searxng/dependabot/pip/master/splinter-0.16.0

Bump splinter from 0.15.0 to 0.16.0

requirements-dev.txt

@@ -3,7 +3,7 @@ nose2[coverage_plugin]==0.10.0
 cov-core==1.15.0
 pycodestyle==2.8.0
 pylint==2.11.1
-splinter==0.15.0
+splinter==0.16.0
 selenium==3.141.0
 twine==3.4.2
 Pallets-Sphinx-Themes==2.0.1