v0.4.0

• Added two new command-line args for AST formatting. Note that these are experimental and may be removed.
• Removed --config option in favor of .jsfmtrc and better docs around rc.
• Updated esformatter and using new esformatter plugin for automatic brace insertion.
• Updated style guide to include esformatter changes.
• Fixes and cleanup for shebang.
• Support for variable arguments using ES6 rest syntax.
• General rewrite cleanup.
• Changing exit code to -1 on missing arg failure.
• Updates to rc and other dependencies.