This is a placeholder for future use; .mu_modules will be our moral
equivalent to NPM/Yarn's node_modules directory. I've chosen a dot
since for the most part developers can ignore its existence.
This change adds a few more compiler tests and rearranges some bits and pieces
that came up while doing so. For example, we now issue warnings for incorrect
casing and/or extensions of the Mufile (and test these conditions). As part of
doing that, it became clear the layering between the mu/compiler and mu/workspace
packages wasn't quite right, so some logic got moved around; additionally, the
separation of concerns between mu/workspace and mu/schema wasn't quite right, so
this has been fixed also (workspace just understands Mufile related things while
schema understands how to unmarshal the specific supported extensions).
This change recognizes .yml in addition to the official .yaml extension,
since .yml is actually very commonly used. In addition, while in here, I've
centralized more of the extensions logic so that it's more "data-driven"
and easier to manage down the road (one place to change rather than two).
This adds a bunch of general scaffolding and the beginning of a `build` command.
The general engineering scaffolding includes:
* Glide for dependency management.
* A Makefile that runs govet and golint during builds.
* Google's Glog library for logging.
* Cobra for command line functionality.
The Mu-specific scaffolding includes some packages:
* mu/pkg/diag: A package for compiler-like diagnostics. It's fairly barebones
at the moment, however we can embellish this over time.
* mu/pkg/errors: A package containing Mu's predefined set of errors.
* mu/pkg/workspace: A package containing workspace-related convenience helpers.
in addition to a main entrypoint that simply wires up and invokes the CLI. From
there, the mu/cmd package takes over, with the Cobra-defined CLI commands.
Finally, the mu/pkg/compiler package actually implements the compiler behavior.
Or, it will. For now, it simply parses a JSON or YAML Mufile into the core
mu/pkg/api types, and prints out the result.
