Fixing call chaining for before*, after*, it.only, and describe.only

[nbrownus]

For BDD style test suites you could not do .timeout() or anything else after any of these functions. This fixes that, especially important for it.only().

[tj]

why not do this.timeout(n) in the test case etc?

[nbrownus]

Main reason for this patch is that describe and it allow chaining making it odd that not everything follows that convention. It is more of an issue when using .only since there may already be other calls chained and not having this patch results in an error on the definition of the suite or test.

[travisjeffery]

Fixed it.only, describe.only. I don't see the point of before, after.