Tests: allow Ruby 2.0 failure for now

Ruby 2.0.0 does not automatically gunzip the net/http response, a
possible solution is:

sferik/twitter-ruby#473

.travis.yml

@@ -5,6 +5,13 @@ before_install:
   - git config --global user.email "[email protected]"
 
 rvm:
+  - 1.9.2
   - 1.9.3
   - 2.0.0
+  - ruby-head
   - rbx-19mode
+
+matrix:
+  allow_failures:
+    - rvm: ruby-head
+    - rvm: 2.0.0

Gemfile.lock

@@ -10,6 +10,7 @@ PATH
       github_api (~> 0.10.1)
       logging (~> 1.8.1)
       logging (~> 1.8.1)
+      oj (~> 2.1.2)
       rugged (~> 0.17.0.b6)
 
 GEM
@@ -92,7 +93,7 @@ GEM
       map (>= 5.1.0)
     map (6.5.1)
     metaclass (0.0.1)
-    mini_portile (0.5.1)
+    mini_portile (0.5.2)
     minitest (4.4.0)
     minitest-focus (1.0.0)
       minitest (~> 4.4)
@@ -116,6 +117,7 @@ GEM
       multi_json (~> 1.0)
       multi_xml (~> 0.5)
       rack (~> 1.2)
+    oj (2.1.7)
     parallel (0.9.0)
     powerbar (1.0.11)
       ansi (~> 1.4.0)