message: Adds password validation (min 8 characters + min 1 digit/special character)
diff: <input mdInput type="password" formControlName="password" placeholder="Password"/>
  <div *ngIf="registerForm.controls.password.touched">
  <small *ngIf="registerForm.controls.password.hasError('required')" class="text-danger">Password is required</small>
  - <small *ngIf="registerForm.controls.password.hasError('minlength') || registerForm.controls.password.hasError('pattern')" class="text-danger">Password must have at least 8 characters which contain one special character or digit</small>
  + <small *ngIf="registerForm.controls.password.hasError('pattern')" class="text-danger">Password must have at least 8 characters which contain one special character or digit</small>
  </div>
  </md-input-container>
  <md-input-container>
  