Use config_file, include backend module depending on config (closes #8)

Gemfile.lock

@@ -1,16 +1,13 @@
 GEM
   remote: http://rubygems.org/
   specs:
-    activesupport (3.2.2)
-      i18n (~> 0.6)
+    activesupport (3.2.13)
+      i18n (= 0.6.1)
       multi_json (~> 1.0)
-    airbrake (3.0.9)
-      activesupport
-      builder
-    backports (2.3.0)
+    backports (3.3.0)
     beefcake (0.3.7)
     builder (3.1.3)
-    eventmachine (0.12.10)
+    eventmachine (1.0.3)
     i18n (0.6.1)
     kgio (2.7.4)
     m (1.2.1)
@@ -22,9 +19,9 @@ GEM
     purdytest (1.0.0)
       minitest (~> 2.2)
     rack (1.5.2)
-    rack-protection (1.1.4)
+    rack-protection (1.5.0)
       rack
-    rack-test (0.6.1)
+    rack-test (0.6.2)
       rack (>= 1.0)
     raindrops (0.10.0)
     rake (0.9.2.2)
@@ -33,18 +30,18 @@ GEM
       builder (>= 2.1.2)
       i18n (>= 0.4.0)
       multi_json (~> 1.0)
-    sinatra (1.3.1)
-      rack (~> 1.3, >= 1.3.4)
-      rack-protection (~> 1.1, >= 1.1.2)
-      tilt (~> 1.3, >= 1.3.3)
-    sinatra-contrib (1.3.1)
+    sinatra (1.4.2)
+      rack (~> 1.5, >= 1.5.2)
+      rack-protection (~> 1.4)
+      tilt (~> 1.3, >= 1.3.4)
+    sinatra-contrib (1.4.0)
       backports (>= 2.0)
       eventmachine
       rack-protection
       rack-test
-      sinatra (~> 1.3.0)
+      sinatra (~> 1.4.2)
       tilt (~> 1.3)
-    tilt (1.3.3)
+    tilt (1.3.7)
     unicorn (4.3.1)
       kgio (~> 2.6)
       rack
@@ -54,7 +51,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  airbrake
+  activesupport
   m
   purdytest
   rake