using byebug with ruby >= 2.0.0

updated gems
refers to #3996

Gemfile

@@ -1,4 +1,8 @@
 source 'https://rubygems.org'
 
 gem 'jekyll', '~> 1.0'
-gem 'debugger'
+if RUBY_VERSION >= '2.0.0'
+  gem 'byebug'
+else
+  gem 'debugger'
+end

Gemfile.lock

@@ -2,20 +2,19 @@ GEM
   remote: https://rubygems.org/
   specs:
     blankslate (2.1.2.4)
+    byebug (3.5.1)
+      columnize (~> 0.8)
+      debugger-linecache (~> 1.2)
+      slop (~> 3.6)
     classifier (1.3.4)
       fast-stemmer (>= 1.0.0)
     colorator (0.1)
     columnize (0.8.9)
     commander (4.1.6)
       highline (~> 1.6.11)
-    debugger (1.6.8)
-      columnize (>= 0.3.1)
-      debugger-linecache (~> 1.2.0)
-      debugger-ruby_core_source (~> 1.3.5)
     debugger-linecache (1.2.0)
-    debugger-ruby_core_source (1.3.5)
     fast-stemmer (1.0.2)
-    ffi (1.9.3)
+    ffi (1.9.6)
     highline (1.6.21)
     jekyll (1.5.1)
       classifier (~> 1.3)
@@ -36,7 +35,7 @@ GEM
     maruku (0.7.0)
     parslet (1.5.0)
       blankslate (~> 2.0)
-    posix-spawn (0.3.8)
+    posix-spawn (0.3.9)
     pygments.rb (0.5.4)
       posix-spawn (~> 0.3.6)
       yajl-ruby (~> 1.1.0)
@@ -46,8 +45,9 @@ GEM
     rb-kqueue (0.2.3)
       ffi (>= 0.5.0)
     redcarpet (2.3.0)
-    safe_yaml (1.0.3)
-    toml (0.1.1)
+    safe_yaml (1.0.4)
+    slop (3.6.0)
+    toml (0.1.2)
       parslet (~> 1.5.0)
     yajl-ruby (1.1.0)
 
@@ -55,5 +55,5 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  debugger
+  byebug
   jekyll (~> 1.0)

src/_plugins/icon_page_generator.rb

@@ -2,7 +2,11 @@
 # Create individual pages for each icon in the FontAwesome set
 
 require 'yaml'
-require 'debugger'
+if RUBY_VERSION >= '2.0.0'
+  require 'byebug'
+else
+  require 'debugger'
+end
 
 module Jekyll