Operation AsObservable
Operators Skip, SkipLast, Take with time
Removed ObserverBase
Merge pull request #694 from Netflix/docs

Change page from "Mathematical Operators" to "Mathematical and Aggregate Operators"
Merge pull request #689 from akarnokd/ObserverBaseLess

Removed ObserverBase
Merge pull request #664 from akarnokd/OperationAsObservable

Operation AsObservable
Remove ObserverBase Import

Was unused and causing build break once that class was removed.
Manual Merge github.com:akarnokd/RxJava SkipTakeTimed2

Conflicts:
	rxjava-core/src/main/java/rx/Observable.java
	rxjava-core/src/main/java/rx/operators/OperationTakeLast.java
Merge pull request #697 from benjchristensen/skip-take-time-merge

Manual Merge of Pull #667
javadoc improvements:
* diagrams for skip(t), single(), take(t), skipLast(t)
* minor corrections, reformatting of javadoc comments