test: actually test main pkg
etcd: replace -proxy-mode with -proxy
Merge pull request #1106 from bcwaldon/proxy-flag

Replace -proxy-mode=<bool> with -proxy=<enum>
CONTRIBUTING: update link to style guide
proxy: add readonly handler
etcd: add -proxy=readonly
Merge pull request #1112 from bcwaldon/update-link

CONTRIBUTING: update link to style guide
Merge pull request #1110 from bcwaldon/proxy-readonly

Readonly proxy mode
main: add address validation and unix domain socket support