Update dependencies for security issues

Gemfile.lock

@@ -1,35 +1,29 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    activesupport (5.2.1)
-      concurrent-ruby (~> 1.0, >= 1.0.2)
-      i18n (>= 0.7, < 2)
-      minitest (~> 5.1)
-      tzinfo (~> 1.1)
-    concurrent-ruby (1.0.5)
-    faraday (0.15.3)
-      multipart-post (>= 1.2, < 3)
-    faraday_middleware (0.12.2)
-      faraday (>= 0.7.4, < 1.0)
-    gli (2.18.0)
-    hashie (3.6.0)
-    i18n (1.1.0)
-      concurrent-ruby (~> 1.0)
-    minitest (5.11.3)
-    multipart-post (2.0.0)
-    slack-ruby-client (0.13.1)
-      activesupport
-      faraday (>= 0.9)
-      faraday_middleware
+    faraday (2.5.1)
+      faraday-net_http (>= 2.0, < 3.1)
+      ruby2_keywords (>= 0.0.4)
+    faraday-mashify (0.1.0)
+      faraday (~> 2.0)
+      hashie
+    faraday-multipart (1.0.4)
+      multipart-post (~> 2)
+    faraday-net_http (3.0.0)
+    gli (2.21.0)
+    hashie (5.0.0)
+    multipart-post (2.2.3)
+    ruby2_keywords (0.0.5)
+    slack-ruby-client (1.1.0)
+      faraday (>= 2.0)
+      faraday-mashify
+      faraday-multipart
       gli
       hashie
       websocket-driver
-    thread_safe (0.3.6)
-    tzinfo (1.2.5)
-      thread_safe (~> 0.1)
-    websocket-driver (0.7.0)
+    websocket-driver (0.7.5)
       websocket-extensions (>= 0.1.0)
-    websocket-extensions (0.1.3)
+    websocket-extensions (0.1.5)
 
 PLATFORMS
   ruby
@@ -38,4 +32,4 @@ DEPENDENCIES
   slack-ruby-client
 
 BUNDLED WITH
-   1.16.1
+   2.3.17