add ensure_destroy

check status after destroy and change @status

destroy: less http requests per call
ensure_destroy: can be call more than one times
add keypair model
secret_key can be nil
connection can be removed
do not cache connection twice
remove activesupport
change default image id
update gems
upgrade to 0.0.2
add release file
Merge branch 'version_0_0_2'

* remove activesupport dependency
* change default image id