api,service: proxyed requests to services correctly handling headers

We now use net/http/httputil ReverseProxy implementation which correctly
handle re-sending headers and reading them back from the response.
docs: release notes for 0.8.1 version
service: proxied requests preserve host from endpoint url
docs: release nodes for 0.8.2
bump version to 0.8.2
docs/releases/tsr: fix version in the 0.9.0 note
cmd: return true if supported version is equal to current version without iterating.
Merge branch 'master' of https://github.com/tsuru/tsuru
Merge pull request #966 from albertoleal/master

Return true if supported version is equal to current version without iterating over the list.
auto scale: improved autoscale down test.

related to #154.
auto scale: added method to run auto scale.
Merge branch 'master' of github.com:tsuru/tsuru into autoscale
auto scale: added Action and AutoScaleConfig types.

related to #154.