Support creation outside of $GOPATH/src

[prao2-infoblox]

As it stands, atlas-cli doesn't create projects outside of the $GOPATH/src directory.
Since Go modules makes it optional for projects to be present in $GOPATH, I feel atlas-cli should support creating projects in any directory.

This is the error it throws:

Unable to initialize application: formatting error: project must be initialized inside $GOPATH/src directory or below