Examples in README are incorrect

[jf-li00]

Hi! I found some incorrect or improper description of the Installing LTL-Fuzze and Example Usage parts in README:

The directory should be llvm_mode instead of llvm-mode

For some env vars to represent paths, the slash is redundant

export LTLFuzzer=~/LTL-Fuzzer/
export SUBJECT=$LTLFuzzer/experiment/Problem1/

Then if we echo $SUBJECT, it turns out ~/LTL-Fuzzer//experiment/Problem1/ with two slashes together

Besides, in some shells , the exclamation mark in double quotes won't be treated as literal(for example, if you use bash and log in as root this will happen), so single quote might be a better choice.