fix: Gemfile & Gemfile.lock to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-RUBY-ACTIVESUPPORT-569598

Gemfile.lock

@@ -1,20 +1,20 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    activemodel (5.1.4)
+    activemodel (5.2.4.3)
-      activesupport (= 5.1.4)
+      activesupport (= 5.2.4.3)
-    activerecord (5.1.4)
+    activerecord (5.2.4.3)
-      activemodel (= 5.1.4)
+      activemodel (= 5.2.4.3)
-      activesupport (= 5.1.4)
+      activesupport (= 5.2.4.3)
-      arel (~> 8.0)
+      arel (>= 9.0)
-    activesupport (5.1.4)
+    activesupport (5.2.4.3)
       concurrent-ruby (~> 1.0, >= 1.0.2)
-      i18n (~> 0.7)
+      i18n (>= 0.7, < 2)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
-    addressable (2.5.2)
+    addressable (2.7.0)
-      public_suffix (>= 2.0.2, < 4.0)
+      public_suffix (>= 2.0.2, < 5.0)
-    arel (8.0.0)
+    arel (9.0.0)
     aws-sdk (2.10.53)
       aws-sdk-resources (= 2.10.53)
     aws-sdk-core (2.10.53)
@@ -34,14 +34,15 @@ GEM
       xpath (~> 2.0)
     cliver (0.3.2)
     coderay (1.1.2)
-    concurrent-ruby (1.0.5)
+    concurrent-ruby (1.1.6)
     database_cleaner (1.6.1)
     diff-lcs (1.3)
     dotenv (2.2.1)
-    factory_girl (4.8.0)
+    factory_girl (4.9.0)
       activesupport (>= 3.0.0)
     ffi (1.9.18)
-    i18n (0.8.6)
+    i18n (1.8.2)
+      concurrent-ruby (~> 1.0)
     jmespath (1.3.1)
     launchy (2.4.3)
       addressable (~> 2.3)
@@ -52,9 +53,10 @@ GEM
     method_source (0.9.0)
     mini_mime (0.1.4)
     mini_portile2 (2.3.0)
-    minitest (5.10.3)
+    minitest (5.14.1)
     multi_json (1.12.2)
-    mustermann (1.0.1)
+    mustermann (1.1.1)
+      ruby2_keywords (~> 0.0.1)
     nokogiri (1.8.1)
       mini_portile2 (~> 2.3.0)
     poltergeist (1.16.0)
@@ -64,8 +66,8 @@ GEM
     pry (0.11.1)
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
-    public_suffix (3.0.0)
+    public_suffix (4.0.5)
-    rack (2.0.3)
+    rack (2.2.2)
     rack-protection (2.0.0)
       rack
     rack-test (0.7.0)
@@ -89,14 +91,15 @@ GEM
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.6.0)
     rspec-support (3.6.0)
+    ruby2_keywords (0.0.2)
     ruby_dep (1.5.0)
     sinatra (2.0.0)
       mustermann (~> 1.0)
       rack (~> 2.0)
       rack-protection (= 2.0.0)
       tilt (~> 2.0)
-    sinatra-activerecord (2.0.13)
+    sinatra-activerecord (2.0.18)
-      activerecord (>= 3.2)
+      activerecord (>= 4.1)
       sinatra (>= 1.0)
     sinatra-contrib (2.0.0)
       backports (>= 2.0)
@@ -113,14 +116,14 @@ GEM
     sqlite3 (1.3.13)
     temple (0.8.0)
     thread_safe (0.3.6)
-    tilt (2.0.8)
+    tilt (2.0.10)
-    tzinfo (1.2.3)
+    tzinfo (1.2.7)
       thread_safe (~> 0.1)
     tzinfo-data (1.2017.2)
       tzinfo (>= 1.0.0)
-    validate_url (1.0.2)
+    validate_url (1.0.11)
       activemodel (>= 3.0.0)
-      addressable
+      public_suffix
     websocket-driver (0.7.0)
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.2)
@@ -131,12 +134,12 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  activerecord
+  activerecord (>= 5.2.4.3)
   aws-sdk (~> 2)
   bigdecimal
   database_cleaner
   dotenv
-  factory_girl
+  factory_girl (>= 4.8.0)
   launchy
   poltergeist
   pry
@@ -144,13 +147,13 @@ DEPENDENCIES
   rerun
   rspec
   sinatra
-  sinatra-activerecord
+  sinatra-activerecord (>= 2.0.13)
   sinatra-contrib
   sinatra-flash
   slim
   sqlite3
   tzinfo-data
-  validate_url
+  validate_url (>= 1.0.2)
 
 BUNDLED WITH
-   1.15.3
+   1.17.3