Add field attributes (aliases, ignore, rename) for derive FormatArgs#2

Open

smith61 wants to merge 2 commits intoSpaceManiac:masterfrom

Commits on Jun 1, 2017

Implement attributes for renaming and ignoring fields and adding field aliases.
smith61
committed

Commits on Jun 2, 2017

Add tests for code generation with structs/tuples/unit.
smith61
committed