update version to 0.6.0

update gems

update jquery.min.js file

update gems on docs group

upgrade javascript dependencies

pushstream.js: remove handling of the 'unload' event

fix #304 removing a variable that was being set but not used, causing a compilation warn/error

fix #301 adding support to Nginx 1.23

update version to 0.5.5

update copyright years

update ruby and gems versions

fix #293 improve the calculation for the internal structures at shared memory

refactor logic to delete channels avoiding deadlock when same long polling connection is using 2 or more channels sharing the lock

fix channel mutex usage to use all

update ruby and gems versions for tests and ensure tests are working