Partial fix to circular deps (#40)

- Adding tests
- fixing use of set fetching to find repeated deps and prevent infinite
  loops

On a circular loop rebar3 now fails with `{error, no_sort}`, which is
uncaught and should be handled to consider the issue fully fixed.
Return cycles in deps solver
Handle cycle errors in provider
Merge pull request #44 from rebar/fix-circular-deps

Partial fix to circular deps (#40)
output message when starting install_deps provider
don't store global state variables in opts dict
don't use lock file for non-defualt profile deps
remove relx.config from release template
fix relx included rebar config typo
in relx call only include deps dirs if they exist
in relx tar call only include deps dirs if they exist
fix defaults for relx template
don't lose defualt deps when creating current profile
only add lock if default profile