[Gemfile] Install and remove dependency on letters gem.

Letters was causing issues with the colored gem and apparently is not supported
on 1.8.7.

Gemfile

@@ -17,7 +17,6 @@ group :debugging do
   gem "kicker", :git => "https://github.com/alloy/kicker.git", :branch => "3.0.0"
   gem "awesome_print"
   gem "pry"
-  gem "letters"
 end
 
 group :documentation do

Gemfile.lock

@@ -26,7 +26,7 @@ PATH
       octokit (~> 1.7)
       open4 (~> 1.3.0)
       rake (~> 0.9.0)
-      xcodeproj (>= 0.3.4)
+      xcodeproj (~> 0.3.4)
 
 GEM
   remote: http://rubygems.org/
@@ -39,16 +39,7 @@ GEM
     bacon (1.1.0)
     coderay (1.0.8)
     colored (1.2)
-    colorize (0.5.8)
-    columnize (0.3.6)
     crack (0.3.1)
-    debugger (1.2.0)
-      columnize (>= 0.3.1)
-      debugger-linecache (~> 1.1.1)
-      debugger-ruby_core_source (~> 1.1.3)
-    debugger-linecache (1.1.2)
-      debugger-ruby_core_source (>= 1.1.1)
-    debugger-ruby_core_source (1.1.3)
     escape (0.0.4)
     faraday (0.8.4)
       multipart-post (~> 1.1)
@@ -58,12 +49,6 @@ GEM
     hashie (1.2.0)
     i18n (0.6.1)
     json (1.7.5)
-    letters (0.3.1)
-      activesupport
-      awesome_print
-      colorize
-      debugger
-      xml-simple
     listen (0.5.3)
     metaclass (0.0.1)
     method_source (0.8)
@@ -94,7 +79,6 @@ GEM
     webmock (1.8.11)
       addressable (>= 2.2.7)
       crack (>= 0.1.7)
-    xml-simple (1.1.1)
     yard (0.8.2.1)
 
 PLATFORMS
@@ -106,7 +90,6 @@ DEPENDENCIES
   cocoapods!
   github-markup
   kicker!
-  letters
   mocha (~> 0.11.4)
   mocha-on-bacon
   pry

lib/cocoapods.rb

@@ -58,6 +58,5 @@ module Pod
 end
 
 if ENV['COCOA_PODS_ENV'] == 'development'
-  require 'letters'
   require 'awesome_print'
 end