Service inspector closes without flags.
Merge pull request #250 from jaycee/fix-broken-inspector-close

This resolves a simple bug wherein the service inspector (absent flags) would not close after deploying a service; this was simply because the original call to .destroy was no longer made, even without the state flag.

I've not bothered adding tests, as this code will only live for a short while (e.g. the end of this week). In the meantime, we would like comingsoon to still work.

QA
This branch must be QAed against the state flag and without flags. In both cases, after deploying a service, you should be able to close that service's inspector using the close button.
Support tags and root-disk constraints.
Merge pull request #246 from frankban/tags-constraint

Add support for setting/retrieving the missing
constraints: "tags" and "root-disk".

Fix a bug preventing constraints to be removed
in sandbox mode.
Also improve the constraints validation
performed before sending the API requests.

Note that currently bug 1309449 [1] prevents
tags to be removed when using a real juju-core
environment.

QA:
QA must be done in sandbox mode and real env [2].
It involves deploying charms, setting constraints
(including the new ones), changing and removing
them, to see if the backend reacts correctly.
When setting tags, ensure they are normalized (
e.g.: "foo bar, spam," is turned into "foo-bar,spam").
Also, please make sure that constraints are
preserved when exporting/importing bundles, whether
they are set or missing/removed.


[1] https://bugs.launchpad.net/juju-core/+bug/1309449
[2] E.g. by using juju-quickstart to deploy the GUI,
    then running `juju set juju-gui juju-gui-source="https://github.com/frankban/juju-gui.git tags-constraint"` and then waiting for the GUI
    to be ready.