node: fix regression from 09bc16a0

The fix for gh-302 did not reuse the instance's connection which is
crucial to ensure the same connection parameters are used (ie region,
proxy, etc.).

Updated EasyEC2 to accept the connection object as an optional kwarg.
Updated Node.__init__ to pass the instance's connection object to
EasyEC2.

closes gh-307
bump version to 0.94.2
Changelog: add 0.94.2 hotfix changes
Merge branch 'hotfix-0.94.2'