(PDOC-74) Update gemspec not to rely on metadata

Prior to this commit, the gemspec for strings relied on the module
metadata.json. Since we would ultimately like to stop releasing
strings as a module entirely, update the gemspec not to rely on the
module metadata so it is not broken when we ultimately remove it.

puppet-strings.gemspec

@@ -1,16 +1,11 @@
-require 'json'
-
-puppet_metadata = JSON.load File.open(File.expand_path(File.join(__FILE__, '..', 'metadata.json'))).read
-
 Gem::Specification.new do |s|
   s.name = 'puppet-strings'
-
-  %w(author version license summary).each do |section|
-    s.send("#{section}=", puppet_metadata[section])
-  end
-
+  s.author = 'Puppet Labs'
+  s.version = '0.4.0'
+  s.license = 'Apache-2.0'
+  s.summary = 'Puppet documentation via YARD'
   s.email = 'info@puppetlabs.com'
-  s.homepage = puppet_metadata['project_page']
+  s.homepage = 'https://github.com/puppetlabs/puppetlabs-strings'
   s.description = s.summary
   s.files = Dir['lib/**/*'].reject { |f| f if File.directory?(f) }