replace assert($x is Y) with $x as Y

Match "typedef" as a kind in the fallback handler (hhvm#62)

* Match "typedef" as a kind in the fallback handler

This switch cause a RuntimeException for not being exhaustive.

* Comment typo, wrong env var

support Composer 2.0 (hhvm#61)

Remove TravisCI configuration

replace $GLOBALS with \HH\global_get()

don't use is_* functions for arrays

is_array not supported in HHVM 4.71+
others not supported before HHVM 4.45
is/as expressions work across all versions

we don't care about the exact array type here, so using the most generic available interface everywhere

array -> v/darray typehints

Don't raise varray notices on HHVM 4.58

Stop attempting to remove SPL autoloaders

The SPL autoload mechanism has been removed in current nightlies, so
this fails to typecheck.

delete ComposerImporter (hhvm#50)

Also removes:

- `autoloadFilesBehavior` config option (this is backwards compatible because invalid keys are ignored -- I also updated tests to check for that)
- all filters
- leftover test fixtures

Also updates README.

This should be a new major release (hhvm-autoload 3.0.0)