remove explicit require to buffer

A variable `Buffer` is provided by the module system, so this is not
required.
test with published test vectors
support getHashes() method
delete unneeded test
update test vectors
use test vectors for pbkdf2
skip the pbkdf2 test that will take way too long
remove non browser tests
update tests
run all tests in the browser
2.1.7
Merge branch 'master' of github.com:sokra/crypto-browserify
2.1.8