Add rspec

Gemfile.lock

@@ -6,7 +6,21 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
+    diff-lcs (1.4.4)
     rake (12.3.2)
+    rspec (3.10.0)
+      rspec-core (~> 3.10.0)
+      rspec-expectations (~> 3.10.0)
+      rspec-mocks (~> 3.10.0)
+    rspec-core (3.10.1)
+      rspec-support (~> 3.10.0)
+    rspec-expectations (3.10.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.10.0)
+    rspec-mocks (3.10.2)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.10.0)
+    rspec-support (3.10.2)
 
 PLATFORMS
   ruby
@@ -14,6 +28,7 @@ PLATFORMS
 DEPENDENCIES
   imbecile!
   rake (~> 12.0)
+  rspec (~> 3.0)
 
 BUNDLED WITH
    2.1.4