testing, issue #1104: Make the test use static flags
Added version checker interface
inserted setUserAgent in each HTTP request
added APIVersion when call NewRegistry
Insert version checkers when call NewRegistry()
added client's kernel version
Removed an unnecessary error check.
Removed an unnecessary nil assignment
format in the user agent header should follow RFC 2616
reduce the number of string copy operations.
wip
Hack: use helper functions in tests for less copy-pasting
Merge branch 'master' into new_logs
store both logs in a same file, as JSON
add legacy support
add debug and simplify docker logs
documentation.
Make docs build without warnings or errors. Minor additional cleanup.
fix overwrites EXPOSE
add regression test from @crosbymichael