fix: Gemfile & Gemfile.lock to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-RUBY-RACK-569066

Gemfile

@@ -1,6 +1,6 @@
 source 'http://rubygems.org'
 
-gem 'rails', '3.1.1'
+gem 'rails', '5.0.0'
 
 # Bundle edge Rails instead:
 # gem 'rails',     :git => 'git://github.com/rails/rails.git'
@@ -12,16 +12,16 @@ gem 'json'
 # Gems used only for assets and not required
 # in production environments by default.
 group :assets do
-  gem 'sass-rails',   '~> 3.1.4'
-  gem 'coffee-rails', '~> 3.1.1'
+  gem 'sass-rails', '~> 5.0.5'
+  gem 'coffee-rails', '~> 4.1.1'
   gem 'uglifier', '>= 1.0.3'
 end
 
 gem 'json'
 
 gem 'atom'
-gem 'jquery-rails'
-gem "haml-rails"
+gem 'jquery-rails', '>= 4.0.1'
+gem "haml-rails", ">= 0.5.3"
 
 # To use ActiveModel has_secure_password
 # gem 'bcrypt-ruby', '~> 3.0.0'