ExMake 0.1.0

This is another alpha-quality release, adding various bug fixes, enhancements, and optimizations.

Fixes:

• Error out if a phony rule depends on a file that doesn't exist and cannot be built.
• Provide better stack traces in debug mode when an exception is caught in a job runner.
• Fix a pattern match failure that could happen in the Erlang library if a rule had header dependencies.
• Fix the "recipe changed directory" error to actually say what it means.
• Ensure library paths are expanded into absolute paths before adding them.
• Correctly invalidate the environment table cache if a script file changes.

Enhancements:

• Wrap the DAG creation process in a timing pass.
• Add a module for compiling Elixir source code.
• Allow specifying output directory in Erlang rules.
• Add a manifest macro to specify files to be considered sources of the build cache.
• Lift the arbitrary restriction that recurse paths could not contain path separators.
• Change into the directory the file given to --file is located in, and lift a similar separator restriction.

Optimizations:

• Add module caching by using a manifest file in the cache directory.
• If --clear is passed, immediately assume that the cache is stale.

Built with Elixir 0.10.1.