Include tests in dev classmap only and fix its namespace

[simonberger]

This pull request brings two changes regarding tests:

• Fixes the namespace
• Removes them from autoload when used as a vendor or with --no-dev parameter

Addresses: #26

[Oliboy50]

thanks 👌 fixed in => https://github.com/M6Web/Statsd/releases/tag/v1.3.2