Add agent uninstall instructions to Readme#236

tjperry07 wants to merge 2 commits intomasterlogdna/logdna-agent:masterfrom

TID-96-add-agent-uninstall-instructions-to-git-hub-read-melogdna/logdna-agent:TID-96-add-agent-uninstall-instructions-to-git-hub-read-meCopy head branch name to clipboard