Compiled latest google axs_testing.js library (8e35d64)
Reset the log_level to :error in test to avoid test pollution
Make severity of rules configurable

e.g. Capybara::Accessible::Auditor.severe_rules = ['AX_TEXT_02']
With the above configuration, images without alt attributes will now raise an error
Document setup of severe_rules configuration
Use axs_testing that fixes recursion error

See https://github.com/GoogleChrome/accessibility-developer-tools/issues/58
Merge branch 'a11y_57060818_image_without_alt_attributes'