* prevent 'Performing next health check' message being output each loop

* adapt to separated identity, description and state_totals endpoints
* remove multi-process logic (replace later with asyncio?)
* separate logic for different output formats
* make output formats orthogonal
* make --describe and --state-totals orthogonal
* make --color and --state-totals orthogonal
* remove back-compat logic
* use colorama for terminal colors, remove TitleFormatter
* interface changes:
    * subtly tweaked colors
    * automatically use color if terminal supports it
    * remove arguments:
        - remove HOSTS argument
    * remove options:
        -a --all (scan all) option
        -b --no-bold option (use --color=never)
        --print-ports
        --old --old-format
    * renamed options:
        -r -raw --raw-format => --format=raw -f raw
        -j --json --json-format => --format=json -f json
    * transformed options:
        --color => --color=WHEN (use the GNU'esque color opt)

* print over multi lines in the log rather than just str.__repr__
* label --- and +++

* the old `cylc graph` with all of the non-textural stuff stripped out
* no longer dependent on gtk or pygraphviz
* interface changes
  --reference           becomes mandatory
  --file, -f            option removed
  --filter              option removed
  --output-file -O      option removed
  --output-format       option removed

* difference lists and dicts
* differences nested structures
* dictionary order does not affect diff, list order does

* see cylc#2958

* tidy .travis.yml
* run unittests under multiple python versions
* add [pycodestyle] section in tox.ini so pycodestyle can be run with no args

* add --ordered option, results are displayed in order, the cost being that slow results will cause blocking

* ensure order of events not affected by race conditions

* cylc scan will clean up contact files, this may have been the culprit
* reduce the time between the kill and the cylc ping to reduce the window for failure