use bundler/gem_tasks
remove guard
add `rake spec` and get it running
upgrade to Rspec 3
move randomizers shared examples to their own file
correct homepage
remove NumericRandomizer

I can't remember where I was going with it.
move rspec cli options to .rspec
remove #random_value and #value= from randomizers

I decided making dice immutable would be fun.
add build status badge
test on current stable rubies