Break util.cr into multiple files

spec/util_spec.cr

@@ -1,10 +1,10 @@
 require "./spec_helper"
 
-describe "compare_alphanumerically" do
+describe "compare_numerically" do
   it "sorts filenames with leading zeros correctly" do
     ary = ["010.jpg", "001.jpg", "002.png"]
     ary.sort! { |a, b|
-      compare_alphanumerically a, b
+      compare_numerically a, b
     }
     ary.should eq ["001.jpg", "002.png", "010.jpg"]
   end
@@ -12,7 +12,7 @@ describe "compare_alphanumerically" do
   it "sorts filenames without leading zeros correctly" do
     ary = ["10.jpg", "1.jpg", "0.png", "0100.jpg"]
     ary.sort! { |a, b|
-      compare_alphanumerically a, b
+      compare_numerically a, b
     }
     ary.should eq ["0.png", "1.jpg", "10.jpg", "0100.jpg"]
   end
@@ -22,7 +22,7 @@ describe "compare_alphanumerically" do
     ary = ["2", "12", "200000", "1000000", "a", "a12", "b2", "text2",
            "text2a", "text2a2", "text2a12", "text2ab", "text12", "text12a"]
     ary.reverse.sort { |a, b|
-      compare_alphanumerically a, b
+      compare_numerically a, b
     }.should eq ary
   end
 
@@ -30,7 +30,7 @@ describe "compare_alphanumerically" do
   it "handles numbers larger than Int32" do
     ary = ["14410155591588.jpg", "21410155591588.png", "104410155591588.jpg"]
     ary.reverse.sort { |a, b|
-      compare_alphanumerically a, b
+      compare_numerically a, b
     }.should eq ary
   end
 end