Moved the descriptions of some operators to a new "Conditional and Boolean Operators" wiki page.
Merge pull request #639 from Netflix/docs

Moved the descriptions of some operators to a new wiki page.
Fixed the blocking/non-blocking first
Add MSDN links
Mark takeFirst deprecated
Implement the blocking/non-blocking single, singleOrDefault, first, firstOrDefault, last, lastOrDefault
Fix the unit tests in groovy and kotlin