Disable Travis in favor of Circle (#1866)

* replace readme badge

* remove travis config

* move to codecov

* add codecov config

* fix coverage running

scripts/coverage.sh

@@ -1,3 +1,7 @@
 #!/usr/bin/env bash
 
 SOLIDITY_COVERAGE=true scripts/test.sh
+
+if [ "$CI" = true ]; then
+  curl -s https://codecov.io/bash | bash -s
+fi