Move toward the actual REST api w/ json

This patch moves us more toward the rest API in the spec. ping and container
creation are now restificated (with the small caveat that create is currently a
sync response, I will implement async ASAP).

I've defined several helpers (/lxd/response.go) for generating the API-style
response json objects. I've also defined (/client.go) a Response that
represents a response from the API.

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
`go fmt` the patch

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Add ApiCompat and use that instead of ApiVersion in ping

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Merge pull request #53 from tych0/rest-refactoring

Move toward the actual REST api w/ json