Update README.md

small improvements

clarify sensitivity vs scale of noise in elastic sensitivity

bugfix in smoothing for elastic sensitivity

Merge pull request #3 from uber/sm_schema_changes

enable nested column properties

add restricted sensitivity analysis and rewriter

add WPINQ rewriter

rename rewriter package, refactor elastic sensitivity and sample & aggregate rewriters

rewriting rules for histogram bin enumeration

refactor and clean up code

support multiple databases and structured column types in schema

update readme

fix bug in coverage rewriter when grouped column appears after aggregated column

use explicit RelNode create methods