small updates to README with feature matrix and other improvements
fix readme links
Should not write data if the RL/DL is all zeroes
add a bit more pig detail
Merge pull request #73 from aniket486/write_no_data_for_no_RL_DL

Should not write data if the RL/DL is all zeroes
Merge pull request #71 from Parquet/update_readme

Update Readme
Merge pull request #72 from Parquet/schema_compatibility

support for schema compatibility
fix schema compat
Merge branch 'master' into schema_compatibility