issue #29
implemented the pageid interface for page():

````python
ny = wikipedia.page("New York")
other_page = ny.page(pageid=27697009)
````
#29 add more tests (loading actual content)
fix PageError/RedirectionError/DisambiguationError throwing when creating WikipediaPage from pageid
clean up testing for page id
Merge branch 'master' of https://github.com/goldsmith/Wikipedia