Update sequel requirement to >= 5.2, < 5.7 (#163)

Updates the requirements on [sequel](https://github.com/jeremyevans/sequel) to permit the latest version.
- [Changelog](https://github.com/jeremyevans/sequel/blob/master/CHANGELOG)
- [Commits](jeremyevans/sequel@5.4.0...5.6.0)

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

Gemfile.lock

@@ -7,7 +7,7 @@ PATH
       devise (>= 4.3, < 4.5)
       pry (~> 0.11.0)
       rails (~> 5.1.4)
-      sequel (>= 5.2, < 5.5)
+      sequel (>= 5.2, < 5.7)
       sequel-devise (~> 0.0.11)
       sequel-rails (~> 1.0.0)
       sequel_pg (~> 1.8.0)
@@ -82,13 +82,13 @@ GEM
       warden (~> 1.2.3)
     diff-lcs (1.3)
     docile (1.1.5)
-    elasticsearch (6.0.0)
-      elasticsearch-api (= 6.0.0)
-      elasticsearch-transport (= 6.0.0)
-    elasticsearch-api (6.0.0)
+    elasticsearch (6.0.1)
+      elasticsearch-api (= 6.0.1)
+      elasticsearch-transport (= 6.0.1)
+    elasticsearch-api (6.0.1)
       multi_json
     elasticsearch-dsl (0.1.5)
-    elasticsearch-transport (6.0.0)
+    elasticsearch-transport (6.0.1)
       faraday
       multi_json
     erubi (1.7.1)
@@ -99,7 +99,7 @@ GEM
       railties (>= 3.0.0)
     faker (1.8.7)
       i18n (>= 0.7)
-    faraday (0.13.1)
+    faraday (0.14.0)
       multipart-post (>= 1.2, < 3)
     fuubar (2.3.1)
       rspec-core (~> 3.0)
@@ -119,9 +119,9 @@ GEM
     mini_mime (1.0.0)
     mini_portile2 (2.3.0)
     minitest (5.11.3)
-    multi_json (1.12.2)
+    multi_json (1.13.1)
     multipart-post (2.0.0)
-    nio4r (2.2.0)
+    nio4r (2.3.0)
     nokogiri (1.8.2)
       mini_portile2 (~> 2.3.0)
     orm_adapter (0.5.0)
@@ -132,7 +132,7 @@ GEM
     parallel (1.12.1)
     parser (2.5.0.4)
       ast (~> 2.4.0)
-    pg (0.21.0)
+    pg (1.0.0)
     powerpack (0.1.1)
     pry (0.11.3)
       coderay (~> 1.1.0)
@@ -206,7 +206,7 @@ GEM
       ruby-progressbar (~> 1.7)
       unicode-display_width (~> 1.0, >= 1.0.1)
     ruby-progressbar (1.9.0)
-    sequel (5.4.0)
+    sequel (5.6.0)
     sequel-devise (0.0.12)
       devise
       orm_adapter-sequel

ontohub-models.gemspec

@@ -30,7 +30,7 @@ Gem::Specification.new do |s|
   s.add_dependency 'chewy', '~> 0.10.1'
   s.add_dependency 'devise', '>= 4.3', '< 4.5'
   s.add_dependency 'rails', '~> 5.1.4'
-  s.add_dependency 'sequel', '>= 5.2', '< 5.5'
+  s.add_dependency 'sequel', '>= 5.2', '< 5.7'
   s.add_dependency 'sequel-devise', '~> 0.0.11'
   s.add_dependency 'sequel-rails', '~> 1.0.0'
   s.add_dependency 'sequel_pg', '~> 1.8.0'