Add retry_after to SlidingWindow
update dependencies

fix a whole bunch of rspec deprecations in the
process
drop timecop back to 0.6.1

I don't have a specific need for 0.7.x, and it
breaks compatibility with ruby 1.8.
locked wrong timecop version
delete some extra spaces that snuck in there
remove rubinius from travis.yml
cleaning up extra spaces
add :return_retry_after option - defaults to true

determines whether the middleware should return a
Retry-After header. Currently, the default is to
do so - this is a legacy behavior and may be 
changed in the future.
change return_retry_after default to false

Also, the prior version didn't work, because I
was dumb. (Was always set to true). I was thinking
of switching the default to false anyway.
change my website in readme

the prior-referenced site is defunct
Merge branch 'retry_after'