Fixed travis script error reporting

Signed-off-by: Cristian Maglie <[email protected]>

Author: cmaglie

Diff for: .travis.yml

@@ -15,7 +15,9 @@ install:
 script:
   - go build -v arduino.cc/arduino-builder
   - export TEST_PACKAGES=`go list arduino.cc/...`
-  - I=0; for PKG in $TEST_PACKAGES; do go test -v -timeout 30m -covermode=count -coverprofile=coverage.$I.out $PKG; ((I++)); done
+  - RES=0; I=0; for PKG in $TEST_PACKAGES; do go test -v -timeout 30m -covermode=count -coverprofile=coverage.$I.out $PKG; ((RES=RES+$?)); ((I++)); done; ( exit $RES )
+
+after_success:
   - bin/gocovmerge coverage.*.out > coverage.out
   - bin/goveralls -coverprofile=coverage.out -service=travis-ci -repotoken $COVERALLS_TOKEN