new data page and stats
fix errors
change distinct values to distinct count

distinct values can be fetched from the dictionary page
more elaborative wording around is_compressed
Merge branch 'master' into new_data_page_type
Merge branch 'new_data_page_type' of github.com:Parquet/parquet-format into new_data_page_type
updating based on review
Merge branch 'master' into new_data_page_type
address review comments: default value and unused field
Merge pull request #64 from Parquet/new_data_page_type

new data page and stats