Minor grammatical tweaks to C10K, fork-join, scheduling strategy text.

Oliver, I've changed some phrasing and introduced some punctuation; if I've inadvertently obscured the point you were trying to make, please correct. 

I have two issues with the content. First, given Intel's recent paper asserting that proper fork-join is impossible unless it gets built into the core language, the statement that "fork-join ... can easily be implemented" is likely to be challenged. Maybe for that, we _should_ provide some code samples.

Second, while I agree with your claim that a fiber scheduler can implement either a work-stealing or continuation-stealing policy, I'm unclear on how the following sentence supports that: "This is possible because a fiber, when blocked, preserves (in contrast to \tbb) its current stack-frame." Wouldn't both policies be equally possible with stackless, um, resumable functions? I think we might need to say a little more here.