Bump mysql2 from 0.5.4 to 0.5.5

Bumps [mysql2](https://github.com/brianmario/mysql2) from 0.5.4 to 0.5.5.
- [Release notes](https://github.com/brianmario/mysql2/releases)
- [Commits](https://github.com/brianmario/mysql2/compare/0.5.4...0.5.5)

---
updated-dependencies:
- dependency-name: mysql2
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile

@@ -33,7 +33,7 @@ gem 'therubyracer', group: :therubyracer
 
 # Use --without <group> argument to skip unnecessary drivers
 gem 'sqlite3', group: :sqlite
-gem 'mysql2', '~> 0.5.4', group: :mysql
+gem 'mysql2', '~> 0.5.5', group: :mysql
 gem 'pg', '~> 1.4.5', group: :postgresql
 
 group :development do

Gemfile.lock

@@ -174,7 +174,7 @@ GEM
     minitest-stub-const (0.6)
     mocha (2.0.2)
       ruby2_keywords (>= 0.0.5)
-    mysql2 (0.5.4)
+    mysql2 (0.5.5)
     net-imap (0.3.4)
       date
       net-protocol
@@ -364,7 +364,7 @@ DEPENDENCIES
   listen
   minitest-stub-const
   mocha
-  mysql2 (~> 0.5.4)
+  mysql2 (~> 0.5.5)
   pg (~> 1.4.5)
   puma (~> 6.0)
   rack-mini-profiler