Log Message:
ruby-http-form_data: update to 2.0.0.

This version is required by newer ruby-http gem 3.0.0.

Upstream changes: (from CHANGES.md)

## 2.0.0 (2017-10-01)

* [#17](https://github.com/httprb/form_data/pull/17)
  Add CRLF character to end of multipart body.
  [@mhickman][]

## 2.0.0.pre2 (2017-05-11)

* [#14](https://github.com/httprb/form_data/pull/14)
  Enable streaming for urlencoded form data.
  [@janko-m][]

## 2.0.0.pre1 (2017-05-10)

* [#12](https://github.com/httprb/form_data.rb/pull/12)
  Enable form data streaming.
  [@janko-m][]