updated substitute method and added some more functions for pure symbolic execution
concretize
pure symbolic execution is running for integers only
repeated test generation logic for puresymbolic
puresymbolic for integers seems to work
basic string constraints are working for puresymbolic
ToStringPredicate fixed.
Merge remote-tracking branches 'origin/symbolic', 'origin/HEAD' and 'origin/master' into symbolic
regexp.test working in puresymbolic
isFeasible fixed.
hybrid simplifier for symbolic expressions
addAxiom exetended
symbolic functions 2
fixed a bug in addAxiom
fixed two more bugs in addAxiom
fixed a number of bugs related to symbolic functions
regex8.js test is passing for puresymbolic
fromCharCode is working, but charCodeAt is not working
fixed a bug that arises when sym1 - sym2 results in a non-symbolic number.
charCodeAt is partly fixed.  substitute needs to remove all bound variables.