Add shim for collecting logs

Changelog for 0.7.6:

• PR #50 Add shim for collecting logs by @alexellis

The collect command redirects function logs to the journal for
viewing on journalctl. faas-cli logs is not implemented as of
yet. View logs with journalctl -t openfaas-fn:FN_NAME_HERE.

Tested on Dell XPS with Ubuntu Linux. The approach takes
inspiration from the Stellar project.

See the README for more

Commits
2307fc7 Add log shim and collect command by @alexellis
853830c Add shim for collecting logs by @alexellis
262770a Add note for credentials helper by @alexellis
0efb6d4 Update developer docs by @alexellis
27cfe46 Update context on DO by @alexellis
d6c4eba Add help & support by @alexellis
e9d1423 Add terraform sample by @alexellis
4bca5c3 Use 0.7.5 for auth support by @alexellis
10e7a2f Add tutorial for private registry by @alexellis
4775a9a service: support /var/lib/faasd/.docker/config.json by @AkihiroSuda
e07186e deploy: use reference.ParseNormalizedNamed() by @AkihiroSuda

Generated by Derek