Add Linode support

[solocommand]

Resolves #31

@janeczku I'm trying to implement support for Linode, but for some reason I can't get the app to compile (my first experiment in go!). Would you mind reviewing?

rancher-letsencrypt solocommand$ make build
CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags "-X main.Version=v0.5.0 -X main.Git=f71cd2d" -o build/rancher-letsencrypt-linux-amd64
# _/Users/solocommand/Source/rancher-letsencrypt
./context.go:129: unknown field 'LinodeApiKey' in struct literal of type letsencrypt.ProviderOpts
make: *** [build] Error 2

[lukasmalkmus]

In context.go you import this:

import "github.com/janeczku/rancher-letsencrypt/letsencrypt"

But you did your changes in:

import "github.com/solocommand/rancher-letsencrypt/letsencrypt"

[solocommand]

@janeczku Thanks to @lukasmalkmus I was able to resolve the build issue on my machine -- I had the repository checked out to the wrong location for my $GOPATH. That said I'm not sure what the process is or what changes would be required to fix the circle build. I do have the compiled version available in a docker container for testing following the make image process.

[djskinner]

@solocommand I've tested your docker image and it works, nice one!

[djskinner]

Is there a way of disabling test mode?

I'm getting a lot of

14/07/2017 12:10:04time="2017-07-14T11:10:04Z" level=debug msg="Test mode: Forced certificate renewal in 120 seconds"

And its causing rate limiting

[solocommand]

@djskinner yep! I ran into the same issue and created a "production" tag that runs the container without debug mode. Pull that instead of latest and you should be good.

[djskinner]

The 'production' tag works like a charm. Thanks for your work on this.

[djskinner]

What can I do to help get this merged?

[lukasmalkmus]

Make the CircleCI test pass. Looks like it fails because a dependency is missing. I have no glue how dependencies are manage here, but looks like you need to add yours to the file.