maintenance: remove coveralls support

To avoid failure states

Author: psafont

tox.ini

@@ -21,13 +21,11 @@ passenv = CI TRAVIS TRAVIS_*
 deps =
   -rrequirements.txt
   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 =