cleanup Gemfile, move to gemspec

Gemfile

 source 'https://rubygems.org'
 gemspec
-gem "minitest-autotest"
-gem 'autotest-suffix'
-gem 'byebug'

omniauth-sso.gemspec

@@ -8,7 +8,6 @@ Omniauth strategy for "ai's sso"(https://git.autistici.org/ai/sso) based on rbss
   EODESC
   s.authors     = ['Azul']
   s.email       = 'azul@riseup.net'
-  s.files       = Dir['lib/**/*.rb']
   s.homepage    = 'https://0xacab.org/riseup/omniauth-sso'
 
   s.add_runtime_dependency 'omniauth', '~> 1.3'
@@ -16,6 +15,8 @@ Omniauth strategy for "ai's sso"(https://git.autistici.org/ai/sso) based on rbss
 
   s.add_development_dependency 'rake', '>= 10', '< 13'
   s.add_development_dependency 'minitest', '~>5.0'
+  s.add_development_dependency 'minitest-autotest', '~> 1.0'
+  s.add_development_dependency 'autotest-suffix', '~> 1.1'
   s.add_development_dependency 'simplecov', '~> 0.11'
   s.add_development_dependency 'rack-test', '~> 0.6', '>= 0.6.3'
   s.add_development_dependency 'conventional-changelog', '~> 1.2'