First commit of partial RosettaCode contents.

Pushing this for testing purposes. Lots of work still needed.

Task/Entropy/Ruby/entropy-2.rb

@@ -0,0 +1,3 @@
+def entropy2(s)
+  s.each_char.group_by(&:to_s).values.map { |x| x.length / s.length.to_f }.reduce(0) { |e, x| e - x*Math.log2(x) }
+end

Task/Entropy/Ruby/entropy.rb

@@ -0,0 +1,9 @@
+def entropy(s)
+  counts = Hash.new(0)
+  s.each_char { |c| counts[c] += 1 }
+
+  counts.values.reduce(0) do |entropy, count|
+    freq = count / s.length.to_f
+    entropy - freq * Math.log2(freq)
+  end
+end