Add strip_ansi_escape method

lib/rainbow/global.rb

@@ -14,6 +14,10 @@ def self.enabled=(value)
     global.enabled = value
   end
 
+  def self.strip_ansi_escape(string)
+    StringUtils.strip_ansi_escape(string)
+  end
+
 end
 
 def Rainbow(string)

lib/rainbow/string_utils.rb

@@ -16,5 +16,10 @@ def self.wrap_with_sgr(string, codes)
       string
     end
 
+    def self.strip_ansi_escape(string)
+      # See http://www.commandlinefu.com/commands/view/3584/remove-color-codes-special-characters-with-sed
+      string.gsub(/\e\[[0-9;]*[a-zA-Z]/, '')
+    end
+
   end
 end

spec/integration/strip_ansi_escape_spec.rb

@@ -0,0 +1,10 @@
+require 'spec_helper'
+require 'rainbow'
+
+describe 'strip_ansi_escape method' do
+
+  it 'strips ansi escape codes' do
+    expect(Rainbow.strip_ansi_escape("\e[35mhello\e[0m")).to eq 'hello'
+  end
+
+end

spec/unit/string_utils_spec.rb

@@ -58,5 +58,29 @@ class Stringgg < ::String; end
       end
 
     end
+
+    describe '.strip_ansi_escape' do
+      subject { described_class.strip_ansi_escape(string) }
+
+      let(:string) do
+        rainbow = Rainbow.new
+        rainbow.enabled = true
+        rainbow.wrap('hello').
+          foreground(:red).
+          bright.
+          bold.
+          italic.
+          background('#ff8040').
+          underline.
+          color(:blue).
+          blink.
+          inverse.
+          hide
+      end
+
+      it "removes ansi color codes" do
+        expect(subject).to eq 'hello'
+      end
+    end
   end
 end