add writable property to override tags value in Mailbox

It resolve Issue #49
Merge pull request #50 from doortts/fix/issues#49

add writable property to override tags value in Mailbox
Bumped version
Added CONTRIBUTING file
Added additional API tests

Covers all documented functions (new event is missing).
Added test for 'new', use this.server and this.client in tests, fixed some issues with CONDSTORE listing, found and fixed some bugs in Hoodiecrow as well
Bumped version to 1.1.42
move condstore tests to separate file
Do not allow using invalid paths in openMailbox
Merge pull request #5 from andris9/master

上游合并