Allow filters to use any filter type

[optijon]

The docs mention the use of any of the following filter types:

{
  foo: 'bar',          # label=value  (equality)
  foo: { not: 'bar' }, # label!=value (inequality)
  foo: true,           # label=       (presence)
  foo: false,          # label!=      (absence)
  foo: [1, 2],         # label=(1,2)  (any value)
  foo: { not: [1, 2] } # label!=(1,2) (no values)
}

Validation rules prevent these type from being used.

[dzunk]

Good catch, thanks! Can you also add a test case for this here: https://github.com/dzunk/redis-time-series/blob/master/spec/redis/time_series/filters_spec.rb#L83-L101

[dzunk]

Released in https://github.com/dzunk/redis-time-series/releases/tag/0.8.1