Windows test does not pass

## Symptom

* As of 56f6c5f
* Since build [#44](https://travis-ci.org/kangwonlee/tutorial/builds/564609326)
* Goes overtime (>40 min)
* For now, allow Windows tests to fail

## Action plan
* Compare raw logs of build [#48](https://travis-ci.org/kangwonlee/tutorial/builds/564657118) Linux vs Windows
* Check which test of Windows did not pass == test that took too long
* Run that test with stdout capture

Start by comparing the raw logs from Travis builds #44 and #48 for Linux and Windows. Identify which Windows test exceeds 40 minutes, then run that test with stdout capture. Done means the failing or slow test is identified and Windows tests no longer need to be allowed to fail.

索引モデルが issue の本文から書いたものです。