fix readme add saucelabs browser matrix add development section
fix readme
add saucelabs browser matrix
add development section

opbeat/opbeat-react,jahtalab/opbeat-js,opbeat/opbeat-js-core,opbeat/opbeat-angular,jahtalab/opbeat-js,opbeat/opbeat-angular,opbeat/opbeat-angular,opbeat/opbeat-react,opbeat/opbeat-js-core,jahtalab/opbeat-js,opbeat/opbeat-react