Consider making "persistent layering of methods" optional

[j4yk]

The feature implemented for #34 is useful in environments like Lively, but less so in ordinary web applications where methods are seldom or never modified. Since the additional getter call probably adds a performance overhead (which is yet to be measured...), it should be somehow configurable if that technique should be applied or not. In the latter case, the method wrapping should happen as it did before the changes to implement #34.

We could configure this behavior, for example, by adding a configure function or configuration object in the contextjs module.

[j4yk]

Curiously, I can no longer measure the performance drop that we saw in the benchmark chart during the presentation. Although we got the same drop on both @LanDinh's and my machine before the presentation.