Add Require Statement Support

• require(boolean expression, "string"); will terminate a function call, revert all state changes that occurred, and return to the loop state when the boolean expression provided is FALSE
• The method of state rollback is in #4 (closed)
• Require statements are often found in modifiers (#22 (closed))
• This is similar to the IF statements
• We need some way of debugging to ensure that the SMV code is working. This query should help with that (#29)

Solidity Link: https://solidity.readthedocs.io/en/v0.4.24/control-structures.html?highlight=require#error-handling-assert-require-revert-and-exceptions