feature: add coveralls support

Author: psafont

tox.ini

@@ -22,11 +22,13 @@ deps =
   -rrequirements.txt
   py{27,34,35,36}-unit: pytest-cov
   py{27,34,35,36}-unit: codecov
+  py{27,34,35,36}-unit: coveralls
   py{27,34,35,36}-lint: flake8
 
 commands =
   py{27,34,35,36}-unit: python setup.py test --addopts "--cov-report xml --cov cwltool"
   py{27,34,35,36}-unit: codecov
+  py{27,34,35,36}-unit: coveralls
   py{27,34,35,36}-lint: flake8 schema_salad setup.py
 
 whitelist_externals =