support all architectures

[stiltskincode]

This is a proposal for changes.

1. I had problem with terraform and caches. I couldn't use local version of plugin. After upgrade terraform to 1.x.x version, problem disappeared. I added the validator in Makefile for terraform and a version. This is a proposal, and we can also remove it, but If you agree with the proposal I believe this code can be much nicer :) I don't have too much practice in GNU Make
2. Another feature what I have added is a architecture "calculations" for terraform. This system only saved plugin for linux and amd64 what isn't work for mac and osx. Now make file can check architecture for terraform and save provider in a correct directory. I decided to go in this way because I believe directory in terraform.d is similar what they shows with command
   terraform -v

If you agree with this solutions, I will try to improve code In Makefile and also I will update Readme. There is a minor lack of information in readme. I think you cannot do terraform apply if you didn't execute terraform init before (also I will add it)

[stiltskincode]

Also I think we can go with these features as a optional. For instance, instead of "throwing" an error if terraform doesn't exist we can just show an information how to install and so on.

[Cosiek]

👍