Add constants to the class and replace static text with constants

[bocharsky-bw]

No description provided.

[Crisfole]

My first thought about this was "It ought to be an enum", but PHP doesn't have those.

Could you instead use an abstract class with those const values instead? (per: http:https://stackoverflow.com/a/254543/456188).

Something like:

abstract class Level {
  const LEVEL_ERROR = 'error';
  const LEVEL_CRITICAL = 'critical';
  const LEVEL_WARNING = 'warning';
  const LEVEL_INFO = 'info';
}

[Crisfole]

Sorry for the long wait for a response!

If you can fix my comments and get the tests passing I'd love to get this merged! (The comments should actually resolve the test issues).

PS: you can run the unit tests locally with phpunit

[bocharsky-bw]

@Crisfole your comments make sense! I've updated this PR

[Crisfole]

Looks fantastic! Waiting on the tests, if/when they pass I'd say this is a go.

@brianr eyes?

[brianr]

LGTM

[Crisfole]

Merging later today along with a few others and a minor version bump.