update README
options in oasis
removed old files, including Bij,Bencode and some Meta{KB,Prover,...}; removed some deprecation warnings
Util.set_memory_limit, with a C stub to call setrlimit
rigorous method to decide whether to rename a sub-formula
hard time limit (using setrlimit)
merge from dev (better cnf; memory and time limits)
release 0.5.4