Merge tag '0.5.4' into develop

clj-ssh-0.5.4
Updated version for next release cycle
Fix add-identity call in readme
Wrap open-channel exceptions

When .openChannel throws an exception, wrap it in an ex-info exception.  This
allows easier procession of the exceptions in consuming code.
Updated version, release notes and readme for 0.5.5
Merge branch 'release/0.5.5'