fix invalid options --no-ri --no-doc

[ivangabriele]

Replace deprecated --no-ri --no-doc by --no-document.

[thibaudcolas]

Just stumbled upon this today while trying to install the CLI with Ruby v2.6.1.

Here are the errors for reference:

$ gem install travis -v 1.8.9 --no-rdoc --no-ri
ERROR:  While executing gem ... (OptionParser::InvalidOption)
    invalid option: --no-rdoc

✘1 $ gem install travis -v 1.8.9 --no-ri
ERROR:  While executing gem ... (OptionParser::InvalidOption)
    invalid option: --no-ri

[douglascayers]

Fixes #646

[varsnotwars]

ACK. Tested on Windows 10.

[BanzaiMan]

Sorry about that. We merged #707 instead.