small cleanup and quash a compiler warning

- remove unneeded require path from gemspec
- remove unneeded ruby.h include from better_html.h
- fix the C function parameters for Parser#errors, removing unused
  parameter that is generating warnings

better_html.gemspec

@@ -24,7 +24,7 @@ Gem::Specification.new do |s|
   s.extensions    = ['ext/better_html_ext/extconf.rb']
   s.files = Dir["{app,config,db,lib,ext}/**/*", "MIT-LICENSE", "Rakefile", "README.rdoc"]
   s.test_files = Dir["test/**/*"]
-  s.require_paths = ["lib", "ext"]
+  s.require_paths = ["lib"]
 
   s.add_dependency 'ast', '~> 2.0'
   s.add_dependency 'erubi', '~> 1.4'

ext/better_html_ext/better_html.h

@@ -1,2 +1 @@
-#include <ruby.h>
 #include "html_tokenizer.h"

ext/better_html_ext/parser.c

@@ -734,7 +734,7 @@ static VALUE create_parser_error(struct parser_document_error_t *error)
   return rb_class_new_instance(4, args, klass);
 }
 
-static VALUE parser_errors_method(VALUE self, VALUE error_p)
+static VALUE parser_errors_method(VALUE self)
 {
   struct parser_t *parser = NULL;
   VALUE list;