Update error checking
Check gadget string length boundary
Merge pull request #4 from hwchen18546/develop

Use linked list for gadgets chaining
Change the way to search gadgets

 * when you cut different bytes to disassemble,
 * you would get different instructions and more gadgets.
 * Therefore, I change the way to search gadgets
 * by changing disassembly start address
 * which offsets one byte per loop,
 * Each loop would search gadgets from start address to MaxGadgetbyte.