Remove unneeded files from the gem package

There are a bunch of files in the gem package that aren't useful for
downstream projects. Removing these reduces the gem package size from
314K to 293K.

Author: orien

webmachine.gemspec

@@ -31,5 +31,7 @@ Gem::Specification.new do |gem|
   gem.add_development_dependency('webrick', ['~> 1.7.0'])
   gem.add_development_dependency('standard', ['~> 1.21'])
   ignores = File.read('.gitignore').split(/\r?\n/).reject { |f| f =~ /^(#.+|\s*)$/ }.map { |f| Dir[f] }.flatten
-  gem.files = (Dir['**/*', '.gitignore'] - ignores).reject { |f| !File.file?(f) }
+  gem.files = (Dir['**/*', '.gitignore'] - ignores).reject do |f|
+    !File.file?(f) || f.start_with?(*%w[. Gemfile RELEASING Rakefile memory_test spec webmachine.gemspec])
+  end
 end