adding the push value while observed, replay while observed, and push while observed methods
Update observable.md

Adding documentation for the new publish while observed, replay while observed, and publish value while observed methods.
changing the name of the while observed operators to the much more approachable and understandable name share
rearranging order of methods in the documentation after renaming the while observed methods to use the word share
Merge pull request #67 from jhusain/master

Adding share, shareValue, and shareReplay.