Merge pull request duckdb#1478 from hannesmuehleisen/randomfix

Removing rand() from expression executor

Merge pull request duckdb#1352 from hannesmuehleisen/parquetmap2

Required Parquet fields within a list

Merge pull request duckdb#1184 from hannesmuehleisen/rprotect

Fix some R protection bugs

Update .travis.yml

_ instead of - for r package names

Enabling PG to fix test with Python 3.6 (duckdb#778)

Update README in preparation for new website

enabling uploads of release binaries

r package version bump

r package version bump for release