Remove support for legacy Ruby versions

Author: uetchy

.travis.yml

@@ -1,5 +1,3 @@
 language: ruby
 rvm:
-  - 2.1.4
-  - 2.0.0
-  - 1.9.3
+  - 2.2.0

Gemfile

@@ -1,5 +1,7 @@
 source 'https://rubygems.org'
 
 gem 'rake',  :require => false
+
+# Testing
 gem 'rspec', :require => false
 gem 'webmock'

Gemfile.lock

@@ -1,25 +1,26 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    addressable (2.3.6)
+    addressable (2.3.7)
     crack (0.4.2)
       safe_yaml (~> 1.0.0)
     diff-lcs (1.2.5)
-    rake (10.1.0)
-    rspec (3.0.0)
-      rspec-core (~> 3.0.0)
-      rspec-expectations (~> 3.0.0)
-      rspec-mocks (~> 3.0.0)
-    rspec-core (3.0.3)
-      rspec-support (~> 3.0.0)
-    rspec-expectations (3.0.3)
+    rake (10.4.2)
+    rspec (3.2.0)
+      rspec-core (~> 3.2.0)
+      rspec-expectations (~> 3.2.0)
+      rspec-mocks (~> 3.2.0)
+    rspec-core (3.2.1)
+      rspec-support (~> 3.2.0)
+    rspec-expectations (3.2.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.0.0)
-    rspec-mocks (3.0.3)
-      rspec-support (~> 3.0.0)
-    rspec-support (3.0.3)
-    safe_yaml (1.0.3)
-    webmock (1.18.0)
+      rspec-support (~> 3.2.0)
+    rspec-mocks (3.2.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.2.0)
+    rspec-support (3.2.2)
+    safe_yaml (1.0.4)
+    webmock (1.20.4)
       addressable (>= 2.3.6)
       crack (>= 0.3.2)