remove HTTP schema loading in prep for a new way to do this

Some tests will fail until the replacement feature has been implemented.
new user-defined schema loader mechanism
rename downloadSchema to httpLoader
user-defined loader functionality now works
give the user a hint if they provide a loader but try to validate synchronously
rename internal schemas var to _schemas
better README.md
better error message if maxRecursion depth is reached
add test script command-line to package.json
tweak license and mention it in package.json
remove hard-coded JSON-Schema-Test-Suite
add JSON-Schema-Test-Suite as a submodule dependency
blacklist some JSON-Schema-Test-Suite that don’t apply to our implementation

one is a V3 feature that doesn’t apply to V4, one is an optional feature that we don’t support (yet)
look for JSON-Schema-Test-Suite tests in the new location
useful error if JSON-Schema-Test-Suite not found and continue w/other tests