Upgrade to Ruby 2.5.1

The current version of Ruby, 2.3.1, is "In security maintenance phase
(will EOL soon!)", so upgrade to the newest available stable version of
Ruby.

I had to update Webmock as well because the version we were on is
incompatible with Ruby >= 2.4 [1]

The change in `bin/build_summaries.rb` was prompted by a new Rubocop
warning when I switched the target version to 2.5.

[1]: bblimke/webmock#683

.rubocop.yml

@@ -1,6 +1,6 @@
 AllCops:
   DisplayCopNames: true
-  TargetRubyVersion: 2.3
+  TargetRubyVersion: 2.5
 
 Metrics/LineLength:
   Max: 120

.travis.yml

@@ -5,4 +5,4 @@ script:
   - bundle exec rake
 sudo: false
 rvm:
-  - 2.3.1
+  - 2.5.1

Gemfile

@@ -4,7 +4,7 @@ source 'https://rubygems.org'
 
 # Warning: update the README, .travis.yml and TargetRubyVersion in .rubocop.yml
 # if this version is changed:
-ruby '2.3.1'
+ruby '2.5.1'
 
 git_source(:github) { |repo_name| "https://github.com/#{repo_name}.git" }
 
@@ -22,5 +22,5 @@ group :test do
   gem 'pry'
   gem 'rack-test'
   gem 'rubocop'
-  gem 'webmock'
+  gem 'webmock', '~> 3.4.2'
 end

Gemfile.lock

@@ -9,8 +9,8 @@ GIT
 GEM
   remote: https://rubygems.org/
   specs:
-    addressable (2.5.0)
-      public_suffix (~> 2.0, >= 2.0.2)
+    addressable (2.5.2)
+      public_suffix (>= 2.0.2, < 4.0)
     ast (2.4.0)
     autoprefixer-rails (6.7.0)
       execjs
@@ -30,7 +30,7 @@ GEM
     everypolitician-popolo (0.8.0)
       require_all
     execjs (2.7.0)
-    hashdiff (0.3.0)
+    hashdiff (0.3.7)
     json (2.0.3)
     method_source (0.9.0)
     mini_portile2 (2.3.0)
@@ -45,7 +45,7 @@ GEM
     pry (0.11.3)
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
-    public_suffix (2.0.4)
+    public_suffix (3.0.3)
     rack (2.0.5)
     rack-protection (2.0.4)
       rack
@@ -81,7 +81,7 @@ GEM
     tilt (2.0.8)
     tins (1.13.2)
     unicode-display_width (1.3.0)
-    webmock (2.1.0)
+    webmock (3.4.2)
       addressable (>= 2.3.6)
       crack (>= 0.3.2)
       hashdiff
@@ -102,10 +102,10 @@ DEPENDENCIES
   rubocop
   sass
   sinatra
-  webmock
+  webmock (~> 3.4.2)
 
 RUBY VERSION
-   ruby 2.3.1p112
+   ruby 2.5.1p57
 
 BUNDLED WITH
-   1.14.6
+   1.16.5

README.md

@@ -91,14 +91,14 @@ For example, if you are using
 [rbenv](https://cbednarski.com/articles/installing-ruby/):
 
 1. Install the right Ruby version. That would be the version specified at the
-beginning of the Gemfile. For example, if it was `ruby '2.3.1'`, you would type:
+beginning of the Gemfile. For example, if it was `ruby '2.5.1'`, you would type:
 ```bash
-rbenv install 2.3.1
+rbenv install 2.5.1
 rbenv rehash
 ```
 2. Then you would move to the root directory of this project and type:
 ```bash
-rbenv local 2.3.1
+rbenv local 2.5.1
 ruby -v
 ```
 

bin/build_summaries.rb

@@ -43,7 +43,7 @@ def build_slug_to_uuid
 
 def format_date(partial_iso8601)
   return partial_iso8601 if partial_iso8601 =~ /^\d{4}$/
-  if /^\d{4}-\d{2}/ =~ partial_iso8601
+  if /^\d{4}-\d{2}/.match?(partial_iso8601)
     d = Date.parse(partial_iso8601 + '-01')
     return d.strftime('%B %Y')
   end