don't use imp.reload()

this was an attempt at python3 compatibility, but it is causing errors
for some users
prepare for 1.3.4 release
rally: Support for rally landings.
mavproxy: Defaults for rally_breakalt and rally_flags
map: Line drawing to assist with Rally Landing mission planning.
param: Rally pointis lines redrawn upon update of appropriate params.
rally: Can now abort rally landings (more safely).