DRYing up creation of X-Registry-Auth header

Conflicts:
	image.go
Create tar stream for user with specified context dir
Removing support for go1.1
[TRIVIAL] removing extra comment line [ci skip]
Removing comment per feedback
Oops, adding to headers instead of reassigning
add support for ssl connections
add import for crypto/tls
Add ExtraHosts to HostConfig.
Merge pull request #172 from nitrous-io/extra-hosts

Add ExtraHosts to HostConfig
test server: add slash to the name of containers
Merge pull request #174 from mcuadros/master

test server: add slash to the name of containers
Allowing X-Registry-Config header to passed in via the environment
Merge remote-tracking branch 'origin/master' into provide-build-tar-stream-for-user

Conflicts:
	image.go
Adding tests related to building from a contextdir
Adding support for X-Registry-Config header (and corresponding test)
TLSClient testing, versioned api fixed, fake cert and key.
Insecure is default to true
Add ca check, secure connection, renew certificates
documentation changes on TLS clients