v0.2.0

This release removes storage/management of container-based launchers since those were specific to the Kubernetes and Docker Kernel Providers. So only the actual kernel launchers and the respective resource files - which are used (in some form) by all providers - are handled by this base provider.

It also enables the ability for provider subclasses to override find_kernels() in order to perform pre/post operations around the finding of kernels. The Kubernetes Kernel Provider uses this, for example, to ensure its running within a Kubernetes cluster and will not return kernelspecs if outside a cluster.