Use -coverpkg with go test

Our tests aren't being executed recursively, use
this so everything gets run

Resolves #320

.gitignore

@@ -14,4 +14,5 @@ vendor/
 ### Files ###
 #############
 *.ivf
-tags
+tags
+cover.out

.travis.yml

@@ -20,7 +20,8 @@ script:
   - rm -rf examples
   # Remove examples, no test coverage for them
   - golangci-lint run
-  - goveralls -v -race -covermode=atomic -service=travis-ci
+  - go test -coverpkg=$(go list ./... | tr '\n' ',') -coverprofile=cover.out -v -race -covermode=atomic ./...
+  - goveralls -coverprofile=cover.out -service=travis-ci
   - bash .github/assert-contributors.sh
   - bash .github/lint-disallowed-functions-in-library.sh
   - bash .github/lint-commit-message.sh