Signal-analog

* Added Op class in flow.py to allow multiplying and dividing datastreams
to create SignalFlow Functions

* Added Mul and Div combinators for multiplying and dividing streams
* Added "enable" option for publishing a stream. Setting enable=False
will hide that particular stream in a chart/detector.

* Dashboard Group support has been added giving you the ability group sets of
dashboards together in a convenient construct
* Detector support has been added giving you the ability to create detectors
from scratch or re-use the SignalFlow program of an existing Chart
* Dashboards and Charts now update via their `id` instead of by name to
mitigate name conflicts when creating multiple resources with the same name
* Dry-run results are now more consistent between all resources and expose
the API call (sans-headers) that would have been made to use for the given
resource

* Dashboards have learned how to update their child resources (e.g. if you
add a chart in your config, the change will be reflected when you next run
your configuration against SignalFx)
* The CLI builder has learned how to pass dry-run options to its configured resources
* Minor bugfixes for the `signal_analog.flow` module

* Added click to setup.py

* Added CLI builder to create and update dashboard resources