Checking in changes prior to tagging of version v0.4.0

## [v0.4.0](https://github.com/Songmu/timeout/compare/v0.3.1...v0.4.0) (2019-04-21)

* introduce Go Modules [#21](https://github.com/Songmu/timeout/pull/21) ([Songmu](https://github.com/Songmu))

v0.3.1

Checking in changes prior to tagging of version v0.3.1

v0.3.0

Checking in changes prior to tagging of version v0.3.0

v0.2.1

Checking in changes prior to tagging of version v0.2.1

v0.2.0

Checking in changes prior to tagging of version v0.2.0