logrus.TraceLevel should be in v0.6

[amckinney]

The v0.5.1 release adds a reference to logrus.TraceLevel which was released in v1.2.0. Given that your repository doesn't pin its dependencies, this can result in transitive dependency failures.

Instead your #72 should be in a v6.0 release, and you could add an explicit dependency on https://github.com/sirupsen/logrus, i.e. with Go modules and/or dep. Otherwise, this results in an issue when users depend on https://github.com/sirupsen/logrus to ^1.2.0 to mitigate this in the future.

For clarity, a sample error would look something similar to:

./.../vendor/github.com/evalphobia/logrus_sentry/sentry.go:17:3: undefined: logrus.TraceLevel