Bump omniauth from 1.9.1 to 2.1.0

Bumps [omniauth](https://github.com/omniauth/omniauth) from 1.9.1 to 2.1.0.
- [Release notes](https://github.com/omniauth/omniauth/releases)
- [Commits](omniauth/omniauth@v1.9.1...v2.1.0)

---
updated-dependencies:
- dependency-name: omniauth
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Gemfile

@@ -32,7 +32,7 @@ gem 'json-schema', '~> 2.8'
 gem 'librato-metrics', '~> 2.1.2'
 gem 'lograge'
 gem 'mime-types'
-gem 'omniauth', '~> 1.9'
+gem 'omniauth', '~> 2.1'
 gem 'omniauth-facebook', '~> 5.0'
 gem 'omniauth-google-oauth2'
 gem 'p3p', '~> 2.0'

Gemfile.lock

@@ -286,9 +286,10 @@ GEM
       multi_json (~> 1.3)
       multi_xml (~> 0.5)
       rack (>= 1.2, < 3)
-    omniauth (1.9.1)
+    omniauth (2.1.0)
       hashie (>= 3.4.6)
-      rack (>= 1.6.2, < 3)
+      rack (>= 2.2.3)
+      rack-protection
     omniauth-facebook (5.0.0)
       omniauth-oauth2 (~> 1.2)
     omniauth-google-oauth2 (0.5.4)
@@ -519,7 +520,7 @@ DEPENDENCIES
   mini_racer
   mock_redis
   newrelic_rpm
-  omniauth (~> 1.9)
+  omniauth (~> 2.1)
   omniauth-facebook (~> 5.0)
   omniauth-google-oauth2
   p3p (~> 2.0)