unspecified type constraints

[lpena-recurly]

For best practices and for users who implement terragrunt [0]. Type constrains should be added [1]. Without specifying these constraints, applying a terragrunt plan/apply results in type errors [2], depending on the type constraints. Here is a PR that fixes this issue [3].

[0] https://github.com/gruntwork-io/terragrunt
[1] https://www.terraform.io/docs/configuration/variables.html#type-constraints
[2] Invalid value for "inputMap" parameter: lookup() requires a map as the first
argument.
[3] #43

[lpena-recurly]

PR #43 was merged. closing out issue