Track Terragrunt version

[billyfoss]

With the current tag reflecting the terraform version, there have been no updates to inclue newer versions of terragrunt.

This change clarifies where terragrunt vs terraform version is used. It also uses a combined tag so that new builds will be generated when a new version of Terraform or Terragrunt are released.

[ozbillwang]

Thanks for the PR. Please ignore the check failed. I will fix this later.

I am fine for most changes to get the name meaningful.

But for the idea to change the tag from terraform version to terraform version + terragrun version is the way I try to avoid at beginning, because the tag looks mass.

Reasons are:

1. terragrun versions is not big deal, in most case, I can run with old version without issue.
2. I encourage end users to always upgrade their terrafom codes to latest version, with this way, the related terragrun will be newer as well.

One down side is, if no new terraform version is released, we will not upgrade terragrunt as well, if have.

[ozbillwang]

For fixing build check error, please rebase from the master branch (your fork's upstream).

-  if [[ "$TRAVIS_BRANCH" == "master" ]]; then
+  if [[ "$TRAVIS_BRANCH" == "master" && "$TRAVIS_PULL_REQUEST" == false ]]; then

[billyfoss]

Thanks for the review and the build fix. I have rebased the PR. I agree the long tag is complex. I was missing the recent versions of Terragrunt, so I was trying to find a solution for getting those built. I do find it a little confusing for the terragrunt image to be using the terraform version for tagging.

Are there other tagging schemes that might enable the new versions of Terragrunt to get picked up? I also noticed some eks tags and an eks branch. I personally need a GKE version, so I was working on a consistent way to get that in some additional changes.