Log Message:
Update ruby-http-form_data to 1.0.3.

## 1.0.3 (2017-05-18)

* [#16](https://github.com/httprb/form_data/issues/16)
  Fix ruby < 2.0.0 support.
  [@ixti][]

## 1.0.2 (2017-05-08)

* [#5](https://github.com/httprb/form_data.rb/issues/5)
  Allow setting Content-Type non-file parts
  [@abotalov]

* [#6](https://github.com/httprb/form_data.rb/issues/6)
  Creation of file parts without filename
  [@abotalov]

* [#11](https://github.com/httprb/form_data.rb/pull/11)
  Deprecate `HTTP::FormData::File#mime_type`. Use `#content_type` instead.
  [@ixti]