Add listen gem so nano watch works

Gemfile

@@ -12,3 +12,4 @@ gem 'nokogiri'
 gem 'builder'
 gem 'fssm'
 gem 'systemu'
+gem 'listen'

Gemfile.lock

@@ -11,6 +11,7 @@ GEM
       colored (>= 1.2)
     faraday (0.8.7)
       multipart-post (~> 1.1)
+    ffi (1.8.1)
     fssm (0.2.10)
     haml (4.0.2)
       tilt
@@ -20,6 +21,10 @@ GEM
     httpauth (0.2.0)
     jwt (0.1.8)
       multi_json (>= 1.5)
+    listen (1.0.3)
+      rb-fsevent (>= 0.9.3)
+      rb-inotify (>= 0.9)
+      rb-kqueue (>= 0.2)
     mime-types (1.23)
     multi_json (1.7.3)
     multi_xml (0.5.3)
@@ -35,6 +40,11 @@ GEM
       rack (~> 1.2)
     rack (1.5.2)
     rake (10.0.4)
+    rb-fsevent (0.9.3)
+    rb-inotify (0.9.0)
+      ffi (>= 0.5.0)
+    rb-kqueue (0.2.0)
+      ffi (>= 0.5.0)
     rdiscount (2.0.7.3)
     rubypants (0.2.0)
     sass (3.2.8)
@@ -49,6 +59,7 @@ DEPENDENCIES
   builder
   fssm
   haml
+  listen
   mime-types
   nanoc
   nokogiri