fix code smells in web_steps.rb

codeclimate marked generated cucumber code as a code smell i.e when
using assert and should
https://codeclimate.com/github/dtscraft/calcentral_events_prototype/WithinHelpers#
set capybara http timeout to 20s

'rescue in rbuf_fill': Timeout::Error (Timeout::Error)
http://stackoverflow.com/questions/10011387/rescue-in-rbuf-fill-timeouterror-timeouterror
remove code duplication from should/should not

some step definitions in web_steps.rb use should and the steps exact
opposite contains should not. Both steps contain nearly identical
statements except for the assertion