Update readme.md

readme.md

@@ -2,11 +2,32 @@
 *spec your xml*
 
 ## installation
-```ruby Gemfile
+```
+# Gemfile
 gem 'rspec-xml'
 ```
 
 ## Usage
-```ruby some_spec.rb
+
+```ruby
+# some_spec.rb
+"<something>else</something>".should have_xpath('/something')
 "<something>else</something>".should have_xpath('/something').with_text('else')
+
+"<something>else</something>".should_not have_xpath('/what')
+"<something>else</something>".should_not have_xpath('/something').with_text('what')
 ```
+
+### Builder
+
+```ruby
+xml = ''
+builder = Builder::XmlMarkup.new(:target => xml)
+builder.instruct!
+
+builder.some_xml do |xml|
+  xml.inner 'stuff'
+end
+
+xml.should have_xpath('//some_xml/inner').with_text('stuff')
+```