Don't delete contexts when all of them are unavailable

Changelog for v0.0.1-rc3:

Commits
bd329c3 Don't remove if there are zero or no reachable contexts by @alexellis
8ed8704 Add notes on daily trim by @alexellis
f5da53c Add Q&A by @alexellis
d339c6f Add .DEREK.yml file for release notes by @alexellis
9fc7d0c Allow artifact upload by @alexellis
bbf47c6 Inject version to correct package by @alexellis
31c1515 Add README by @alexellis
695923d Initial by @alexellis

Changes: https://github.com/alexellis/kubetrim/commits/v0.0.1-rc3

Generated by Derek