Support query monitorings

[rmatsuoka]

I make mkr support "query monitoring", which is a new monitoring rule on Mackerel.

example

First I have got monitors.json using mkr monitors pull and edited it to add a new query rule new query.
Then, I tested two command diff and push as following.

% ./mkr monitors diff
Summary: 0 modify, 1 append, 0 remove

+{
+  "name": "new query",
+  "type": "query",
+  "query": "http.client.duration.p90{service.name=\"web-app\"}",
+  "operator": "<",
+  "warning": 1,
+  "critical": null,
+  "legend": "{{http.status_code}}"
+},
% ./mkr monitors push
      info Create a new rule.
{
  "name": "new query",
  "type": "query",
  "query": "http.client.duration.p90{service.name=\"web-app\"}",
  "operator": "<",
  "warning": 1,
  "critical": null,
  "legend": "{{http.status_code}}"
},

After that, I checked the new rule was created through https://mackerel.io/my/monitors

[yseto]

seems good.