Update gem dependencies

Gemfile.lock

@@ -12,7 +12,7 @@ GEM
       coderay (>= 1.0.0)
       erubis (>= 2.6.6)
       rack (>= 0.9.0)
-    browser (2.0.2)
+    browser (2.0.3)
     coderay (1.1.1)
     coffee-script (2.4.1)
       coffee-script-source
@@ -27,7 +27,7 @@ GEM
     execjs (2.6.0)
     ffi (1.9.10)
     highline (1.7.8)
-    html-pipeline (2.3.0)
+    html-pipeline (2.4.0)
       activesupport (>= 2, < 5)
       nokogiri (>= 1.4)
     i18n (0.7.0)
@@ -51,14 +51,14 @@ GEM
       rack
     rack-test (0.6.3)
       rack (>= 1.0)
-    rake (11.1.1)
+    rake (11.1.2)
     rr (1.1.2)
-    sass (3.4.21)
+    sass (3.4.22)
     sinatra (1.4.7)
       rack (~> 1.5)
       rack-protection (~> 1.4)
       tilt (>= 1.3, < 3)
-    sinatra-contrib (1.4.6)
+    sinatra-contrib (1.4.7)
       backports (>= 2.0)
       multi_json
       rack-protection
@@ -66,7 +66,7 @@ GEM
       sinatra (~> 1.4.0)
       tilt (>= 1.3, < 3)
     slop (3.6.0)
-    sprockets (3.5.2)
+    sprockets (3.6.0)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
     sprockets-helpers (1.2.1)