[Feature] Update puppetfile/getDependencies

Use Case

PR 255 added the puppetfile/getDependencies

[ ] Update the call to read in the document if it's not already in the cache (or perhaps transfer the entire file content)?
[ ] Create a data contract for the response (What should the repsonse have in it)
[ ] Should the response be a flat list of all modules or a tree based response
[ ] Better error responses for the different types of errors