add support for numeric keys in map literal

[ccutrer]

This supercedes #934 (rebased, and then addresses the review comment), and fixes #1090. Note that I verified Python Jinja accepts numbers as dict keys:

>>> from jinja2 import Environment
>>> env = Environment()
>>> expr = env.compile_expression("{0:'test'}[0]")
>>> expr()
'test'

[apella12]

I'd add that merging this PR would help with global warming.
1) Smart thermostats save energy 2) Home Assistant (a major smart home DIY application) configurations are used by java based smart home applications to control smart thermostats. 3) A sample home assistant smart thermostat configuration uses three instances of numeric keys.

{
  "min_temp": 50,
  "max_temp": 85,
  "modes": [
    "off",
    "heat",
    "cool"
  ],
  "fan_modes": [
    "auto",
    "on"
  ],
  "action_topic": "zwave6/Thermostat_-_63/thermostat_operating_state/endpoint_0/state",
  "current_temperature_topic": "zwave6/Thermostat_-_63/sensor_multilevel/endpoint_0/Air_temperature",
  "current_temperature_template": "{{ value_json.value }}",
  "fan_mode_state_topic": "zwave6/Thermostat_-_63/thermostat_fan_mode/endpoint_0/mode",
  "fan_mode_command_topic": "zwave6/Thermostat_-_63/thermostat_fan_mode/endpoint_0/mode/set",
  "mode_state_topic": "zwave6/Thermostat_-_63/thermostat_mode/endpoint_0/mode",
  "mode_command_topic": "zwave6/Thermostat_-_63/thermostat_mode/endpoint_0/mode/set",
  "temperature_state_template": "{{ value_json.value }}",
  "temperature_command_topic": "zwave6/Thermostat_-_63/thermostat_setpoint/endpoint_0/setpoint/1/set",
  "mode_state_template": "{{ {0: \"off\", 1: \"heat\", 2: \"cool\"}[value_json.value] | default('off') }}",
  "temperature_state_topic": "zwave6/Thermostat_-_63/thermostat_setpoint/endpoint_0/setpoint/1",
  "action_template": "{{ {0: \"idle\", 1: \"heating\", 2: \"cooling\", 3: \"fan\"}[value_json.value] | default('idle') }}",
  "fan_mode_state_template": "{{ {0: \"auto\", 1: \"on\"}[value_json.value] | default('auto') }}",
  "temperature_unit": "F",
  "precision": 0.1,
  "device": {
    "identifiers": [
      "zwavejs2mqtt_0xf1c43721_node63"
    ],
    "manufacturer": "Radio Thermostat Company of America (RTC)",
    "model": "Z-Wave Thermostat (CT101)",
    "name": "Thermostat - 63",
    "sw_version": "9.0"
  },
  "availability": [
    {
      "payload_available": "true",
      "payload_not_available": "false",
      "topic": "zwave6/Thermostat_-_63/status",
      "value_template": "{{'true' if value_json.value else 'false'}}"
    },
    {
      "topic": "zwave6/_CLIENTS/ZWAVE_GATEWAY-zwave-js-ui/status",
      "value_template": "{{'online' if value_json.value else 'offline'}}"
    },
    {
      "payload_available": "true",
      "payload_not_available": "false",
      "topic": "zwave6/driver/status"
    }
  ],
  "availability_mode": "all",
  "name": "Thermostat - 63",
  "unique_id": "zwavejs2mqtt_0xf1c43721_Node63_thermostat"
}

[ccutrer]

Ping @samukce

[ccutrer]

@boulter: any chance we could get a new release cut with this in it?