Deprecated: remove deprecated.rb

[rubyFeedback]

Hi,

Today I studied launchy's code because I wanted to find out how you guys manage
to launch browser on windows.

I also saw this file:

https://github.com/copiousfreetime/launchy/blob/master/lib/launchy/deprecated.rb

I believe it may be better to actually delete the code rather than carry it along the
ride nowadays.