Add type test to TravisCI (#677)
Add type test to TravisCI (#677)

**What**: Add type test to Travis

**Why**: Type modifying PR can make mistakes.

**How**: Add `test:typescript` to `test` script.

**Checklist**:
- [N/A] Documentation
- [x] Tests
- [N/A] Code complete


emotion-js/emotion,tkh44/emotion,tkh44/emotion,emotion-js/emotion,emotion-js/emotion,emotion-js/emotion