Add cluster events CLI

[smurching]

Adds CLI for the cluster events REST API.

Example output (mimics the output format of the clusters UI by default):

$ databricks clusters events --cluster-id 0717-061054-beech1 --profile demo --limit 4
$ databricks clusters events --cluster-id 0717-061054-beech1 --profile demo --limit 4
2019-07-18 00:23:47 PDT  TERMINATING     {'reason': {'code': 'INACTIVITY', 'parameters': {'inactivity_duration_min': '60'}}}
2019-07-17 22:09:49 PDT  DRIVER_HEALTHY  {}
2019-07-17 22:09:32 PDT  RUNNING         {'current_num_workers': 0, 'target_num_workers': 0}
2019-07-17 22:07:13 PDT  STARTING        {'user': 'sid.murching@databricks.com'}

Full REST API JSON output is available by specifying --output json:

{
  "events": [
    {
      "cluster_id": "0717-061054-beech1",
      "timestamp": 1563434627634,
      "type": "TERMINATING",
      "details": {
        "reason": {
          "code": "INACTIVITY",
          "parameters": {
            "inactivity_duration_min": "60"
          }
        }
      }
    },
    {
      "cluster_id": "0717-061054-beech1",
      "timestamp": 1563426589300,
      "type": "DRIVER_HEALTHY",
      "details": {}
    },
    {
      "cluster_id": "0717-061054-beech1",
      "timestamp": 1563426572019,
      "type": "RUNNING",
      "details": {
        "current_num_workers": 0,
        "target_num_workers": 0
      }
    }
  ],
  "next_page": {
    "cluster_id": "0717-061054-beech1",
    "end_time": 1563434627634,
    "offset": 3,
    "limit": 3
  },
  "total_count": 16
}

[codecov-io]

Codecov Report

Merging #238 into master will increase coverage by 0.22%.
The diff coverage is 96.66%.

@@            Coverage Diff             @@
##           master     #238      +/-   ##
==========================================
+ Coverage   82.92%   83.14%   +0.22%     
==========================================
  Files          31       31              
  Lines        1991     2077      +86     
==========================================
+ Hits         1651     1727      +76     
- Misses        340      350      +10

Impacted Files	Coverage Δ
setup.py	0% <ø> (ø)	⬆️
databricks_cli/clusters/cli.py	95.39% <100%> (+1.03%)	⬆️
databricks_cli/clusters/api.py	53.33% <50%> (-0.24%)	⬇️
databricks_cli/runs/cli.py	97.26% <0%> (-1.21%)	⬇️
databricks_cli/runs/api.py	57.14% <0%> (-1.2%)	⬇️
databricks_cli/cli.py	0% <0%> (ø)	⬆️
databricks_cli/dbfs/cli.py	0% <0%> (ø)	⬆️
databricks_cli/click_types.py	94.2% <0%> (+0.86%)	⬆️
databricks_cli/dbfs/api.py	60.55% <0%> (+8.92%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f4a05cb...39502fb. Read the comment docs.