Upgraded nio4r gem + Ruby version

.ruby-version

@@ -1 +1 @@
-2.6.3
+2.6.4

.travis.yml

@@ -1,6 +1,6 @@
 language: ruby
 rvm:
-  - "2.6.3"
+  - "2.6.4"
 
 before_install:
   - "phantomjs --version"

Gemfile

@@ -4,7 +4,7 @@ source "https://rubygems.org"
 #don't upgrade
 gem "rails", "5.1.7"
 
-ruby "2.6.3"
+ruby "2.6.4"
 
 gem "aruba"
 gem "bcrypt"

Gemfile.lock

@@ -173,7 +173,7 @@ GEM
     multi_test (0.1.2)
     mysql2 (0.5.2)
     nenv (0.3.0)
-    nio4r (2.5.0)
+    nio4r (2.5.1)
     nokogiri (1.10.4)
       mini_portile2 (~> 2.4.0)
     notiffany (0.1.3)
@@ -369,7 +369,7 @@ DEPENDENCIES
   unicorn
 
 RUBY VERSION
-   ruby 2.6.3p62
+   ruby 2.6.4p104
 
 BUNDLED WITH
    1.17.3