Merge pull request #192 from searxng/dependabot/pip/master/splinter-0.15.0

Bump splinter from 0.14.0 to 0.15.0

requirements-dev.txt

@@ -3,7 +3,7 @@ nose2[coverage_plugin]==0.10.0
 cov-core==1.15.0
 pycodestyle==2.7.0
 pylint==2.9.3
-splinter==0.14.0
+splinter==0.15.0
 transifex-client==0.14.2
 selenium==3.141.0
 twine==3.4.1