Implemented script to generate isomorphic test cases

testcases/isomorphic_test/L-Theanine_iso.txt

testcases/isomorphic_test/Vitamin-C_iso.txt

testcases/isomorphic_test/acetylene_iso.txt

testcases/isomorphic_test/adenine_iso.txt

testcases/isomorphic_test/biotin_iso.txt

testcases/isomorphic_test/ethanol_iso.txt

testcases/isomorphic_test/glucose_iso.txt

testcases/isomorphic_test/lactose_iso.txt

testcases/isomorphic_test/ribose_iso.txt

testcases/isomorphic_test/sucrose_iso.txt

testcases/molecule_input.py