build(deps-dev): bump mysql2 from 0.5.6 to 0.5.7

Bumps [mysql2](https://github.com/brianmario/mysql2) from 0.5.6 to 0.5.7.
- [Release notes](https://github.com/brianmario/mysql2/releases)
- [Commits](brianmario/mysql2@0.5.6...0.5.7)

---
updated-dependencies:
- dependency-name: mysql2
  dependency-version: 0.5.7
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Gemfile

@@ -63,7 +63,7 @@ gem 'fog-openstack'
 gem 'cf-uaa-lib', '~> 4.0.9'
 
 group :db do
-  gem 'mysql2', '~> 0.5.6'
+  gem 'mysql2', '~> 0.5.7'
   gem 'pg'
 end
 

Gemfile.lock

@@ -340,7 +340,8 @@ GEM
     mustermann (3.0.0)
       ruby2_keywords (~> 0.0.1)
     mutex_m (0.3.0)
-    mysql2 (0.5.6)
+    mysql2 (0.5.7)
+      bigdecimal
     net-ssh (7.3.0)
     netaddr (2.0.6)
     netrc (0.11.0)
@@ -663,7 +664,7 @@ DEPENDENCIES
   mime-types (~> 3.7)
   mock_redis
   multipart-parser
-  mysql2 (~> 0.5.6)
+  mysql2 (~> 0.5.7)
   net-ssh
   netaddr (>= 2.0.4)
   newrelic_rpm