Re-work require statements

Use `require_relative` for all components under Puppetx. This makes it possible
to load `pupetx/yardoc/yard/plugin` outside of Puppet as a YARD plugin.

Also fix the `yardoc` face so that Puppetx bits are loaded _after_ feature
checks.

lib/puppet/face/yardoc.rb

@@ -1,5 +1,4 @@
 require 'puppet/face'
-require 'puppetx/yardoc/yard/parser'
 
 Puppet::Face.define(:yardoc, '0.0.1') do
 
@@ -12,12 +11,12 @@ Puppet::Face.define(:yardoc, '0.0.1') do
         raise RuntimeError, "The 'yard' gem must be installed in order to use this face."
       end
 
-      if Puppet.features.rgen?
-        require 'puppet/pops'
-      else
+      unless Puppet.features.rgen?
         raise RuntimeError, "The 'rgen' gem must be installed in order to use this face."
       end
 
+      require 'puppetx/yardoc/yard/plugin'
+
       parser = Puppetx::Yardoc::YARD::PuppetParser.new(File.read(manifest), manifest)
       parser.parse
 

lib/puppetx/yardoc/pops/yard_statement.rb

@@ -1,7 +1,7 @@
-require 'puppetx/yardoc'
-
 require 'puppet/pops'
 
+require_relative '../../yardoc'
+
 module Puppetx::Yardoc::Pops
   # An adapter class that conforms a Pops model instance + adapters to the
   # interface expected by YARD handlers.

lib/puppetx/yardoc/pops/yard_transformer.rb

@@ -1,7 +1,6 @@
-require 'puppetx/yardoc'
-
 require 'puppet/pops'
 
+require_relative '../../yardoc'
 require_relative 'yard_statement'
 
 module Puppetx::Yardoc::Pops

lib/puppetx/yardoc/yard/handlers/base.rb

@@ -1,7 +1,8 @@
-require 'puppetx/yardoc'
 require 'yard'
 require 'puppet/pops'
 
+require_relative '../../../yardoc'
+
 module Puppetx::Yardoc::YARD::Handlers
   class Base < YARD::Handlers::Base
     include Puppet::Pops::Model # This allows handlers to match based on model classes.

lib/puppetx/yardoc/yard/parser.rb

@@ -1,8 +1,8 @@
-require 'puppetx/yardoc'
-
 require 'yard'
 require 'puppet/pops'
-require 'puppetx/yardoc/pops/yard_transformer'
+
+require_relative '../../yardoc'
+require_relative '../pops/yard_transformer'
 
 module Puppetx::Yardoc::YARD
   class PuppetParser < YARD::Parser::Base