Update xpath lib
Add `exact` option
Add `exact` config option
Add `match` option
Add prefer_exact match strategy which behaves like Capybara 1.x
Fix some specs, due to visibility changes
Fix basics nodes
Merge branch 'capy21'

Conflicts:
	spec/basic_node_spec.rb
Add public key
Ignore private key
Use pry for debugging
Add signing key stuff to gemspec, so I don't forget it

(sorry for the noise to those running edge capy on bundler)
Empty tags are invisible according to Selenium. Huh.