Issue 58: Bump ruby version to 2.4.2

Closes codeforamerica#58. 2.4.2 is the latest version of ruby [supported by Heroku](https://devcenter.heroku.com/articles/ruby-support#supported-runtimes). The current version is causing deploys of this app to Heroku to fail.

This also updates various dependencies in the lockfile using `bundle update #{name}` because of issues related to newer versions of ruby.

- `json` [⚠](ruby/json#286)
- `safe_yaml` [⚠](dtao/safe_yaml#67)
- `webmock` [⚠] (bblimke/webmock#683)

For folks that have this checked out locally, I also had to `brew install --force` to force an up to date build of `http_parse.rb`, which was throwing `Symbol not found: _rb_cFixnum`.

Finally, this updates petharbor cassette to include URL encoded quotes - this is probably just an internal change to `URI.encode_www_form`.

.travis.yml

@@ -1,5 +1,5 @@
 language: ruby
 rvm:
-  - ruby-2.1.2
+  - ruby-2.4.2
 notifications:
   webhooks: http://project-monitor.codeforamerica.org/projects/d702edae-5a33-478b-9d08-acc4a7826533/status

Gemfile

@@ -1,6 +1,6 @@
 source 'https://rubygems.org'
 
-ruby '2.1.2'
+ruby '2.4.2'
 
 gem 'twitter'
 gem 'dotenv'

Gemfile.lock

@@ -1,28 +1,31 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    addressable (2.3.6)
+    addressable (2.5.2)
+      public_suffix (>= 2.0.2, < 4.0)
     buftok (0.2.0)
-    crack (0.4.2)
+    crack (0.4.3)
       safe_yaml (~> 1.0.0)
     dotenv (0.11.1)
       dotenv-deployment (~> 0.0.2)
     dotenv-deployment (0.0.2)
     equalizer (0.0.9)
     faraday (0.9.0)
       multipart-post (>= 1.2, < 3)
+    hashdiff (0.3.6)
     hpricot (0.8.6)
     http (0.6.2)
       http_parser.rb (~> 0.6.0)
     http_parser.rb (0.6.0)
-    json (1.8.1)
+    json (1.8.6)
     memoizable (0.4.2)
       thread_safe (~> 0.3, >= 0.3.1)
     minitest (5.4.1)
     multipart-post (2.0.0)
     naught (1.0.0)
+    public_suffix (3.0.0)
     rake (10.3.2)
-    safe_yaml (1.0.3)
+    safe_yaml (1.0.4)
     simple_oauth (0.2.0)
     thread_safe (0.3.4)
     twitter (5.11.0)
@@ -37,9 +40,10 @@ GEM
       naught (~> 1.0)
       simple_oauth (~> 0.2.0)
     vcr (2.9.3)
-    webmock (1.18.0)
+    webmock (3.0.1)
       addressable (>= 2.3.6)
       crack (>= 0.3.2)
+      hashdiff
 
 PLATFORMS
   ruby
@@ -52,3 +56,9 @@ DEPENDENCIES
   twitter
   vcr
   webmock
+
+RUBY VERSION
+   ruby 2.4.2p198
+
+BUNDLED WITH
+   1.15.4