scanf is no longer bundled with Ruby 2.7.0

[hendrixfan]

Hi there,

I'm using your libary to create triangle patterns and I've noticed that there seems to be an Issue with Ruby 2.7.

When I run bin/console in ruby 2.7 I'm getting the following error:

Traceback (most recent call last):
	5: from bin/console:4:in `<main>'
	4: from bin/console:4:in `require'
	3: from /home/wolle/projekte/gradient/lib/gradient.rb:8:in `<top (required)>'
	2: from /home/wolle/projekte/gradient/lib/gradient.rb:8:in `require'
	1: from /home/wolle/projekte/gradient/lib/gradient/svg.rb:1:in `<top (required)>'
/home/wolle/projekte/gradient/lib/gradient/svg.rb:1:in `require': cannot load such file -- scanf (LoadError)

scanf cannot be loaded because it was excluded as a standard libary as of version 2.7 https://rubyreferences.github.io/rubychanges/2.7.html#libraries-excluded-from-the-standard-library

Solution:

Include scanf in your gemspec