removed dependency from GF256's gf256
added documentation
replaced asserts with a condition throwing an ArithmeticException if violated
GF256 is now using (for now hardcoded) lookup-tables for calculation
create a custom GF256Polynomial which uses the fast arithmetic operations from GF256 for evaluateAt()
added unit-tests for GF256 to allow easier testing of further optimizations (+ typo fix in performance.txt)
lookup-tables not hardcoded anymore (+ add '{}')
added newlines at end of files