Added option clear_site_dir to removed old files from site directory
merged before pull request to sync with upstream
Fixed syntax error
Fixed another Python 3 syntax error
Fixed whitespace issues reported by flake8 test
Merge remote-tracking branch 'upstream/master' into feature/clear-site-directory-option

Synced with upstream
Removed clear_site_dir option and made it the default behaviour
Fixed bug in clear_directory (fails if directory does not exist)
Removed exception handling as suggested by d0ugal
Clear directory for json builds as well
Added --clean switch to build command and output of stale files warning (with simple check)
Fixed flake8 error (no newline at end of file)
Renamed clear_directory to clean_directory
Enabled clean switch for json and gh-deploy commands as well
Added documentation about new --clean switch
Fixed small typos in release notes
Merge pull request #154 from devbliss/feature/clear-site-directory-option

Clear site directory before build