enable version updates
test refactorings
TEST_SUITE::SPEED.eql? LIGHT::SPEED # => true
use guard and prosper
add convenient methods for gem type checks and fix tests
prefer let! over instance methods in specs

we have to use let! because ordinary let is lazy evaluated and our
examples depend on the result of output

see here for more info:

https://twitter.com/shime_rb/status/350183492556034048