A written agreement to submit any existing controversy to arbitration or a provision in a written contract to submit to arbitration any controversy thereafter arising between the parties is valid, enforceable and irrevocable, save upon such grounds as exist at law or in equity for the revocation of any contract. This chapter also applies to arbitration agreements between employers and employees or between their respective representatives, unless otherwise provided in the agreement. [PL 1967, c. 430 (NEW).]