svg badges
improved README.md

expanded section on `tsd.json`
- added property table
split/expanded Privacy not to Privacy & Security, added dev-note
tuned link-command section
tuned init-command section
various small tweaks
added test/README.md note
added clean:cruft target
added test/README.md note
migrated config validation to Joi

removed json-schema functionality
- dropped tv4, tv4-reporter, chai-json-schema dependencies & typings
- dropped xm/jsonSchema
- added Joi config schema
- reworked Config validation code
- added many tests
- applied changes to related files

dropped js-yaml dependency

bumped pre-release version to v0.6.0-alpha.2

made some other small changes & cleanups