Add gnome sort

sorting/gnome_sort.rb

@@ -0,0 +1,12 @@
+def gnome_sort(arr)
+  i = 0
+  while i < arr.length
+    if i == 0 || arr[i] >= arr[i - 1]
+      i += 1
+    else
+      arr[i], arr[i - 1] = arr[i - 1], arr[i]
+      i -= 1
+    end
+  end
+  arr
+end

sorting/gnome_sort_test.rb

@@ -0,0 +1,11 @@
+require 'minitest/autorun'
+require_relative './sort_tests'
+require_relative './gnome_sort'
+
+class TestGnomeSort < Minitest::Test
+  include SortTests
+
+  def sort(input)
+    gnome_sort(input)
+  end
+end