Before revision:  Energy identities and stability estimates of the discrete problem are proved for a slightly more general problem , that are used to prove optimal order a priori error estimates with minimal regularity requirement . Uniform norm in time error estimates are proved for the constant and linear cases . Numerical experiments are performed to verify the theoretical rate of convergence.
After revision:  The main goal of this paper is to present a simple and straight forward a priori error analysis of optimal order with minimal regularity requirement on the solution. Uniform norm in time error estimates are also proved for the constant and linear cases. To this end, energy identities and stability estimates of the discrete problem are proved for a slightly more general problem , that are used to prove optimal order a priori error estimates with minimal regularity requirement . Uniform norm in time error estimates are proved for the constant and linear cases . Numerical experiments are performed to verify the theoretical rate of convergence.