Don't attempt to truncate postgres views
Don't attempt to truncate postgres views

This ensures that only proper tables are truncated, rather than
attempting to truncate views (which isn't possible).

gentoo/database_cleaner,eliotsykes/database_cleaner,0xCCD/database_cleaner,yangc5/playlister-sinatra-v-000,claptimes5/database_cleaner,yangc5/playlister-sinatra-v-000,stanislaw/database_cleaner,reinaris/database_cleaner,custora/database_cleaner,avalonmediasystem/database_cleaner,yangc5/playlister-sinatra-v-000,yangc5/playlister-sinatra-v-000,DatabaseCleaner/database_cleaner,fajrif/database_cleaner,amorphid/database_cleaner,simonmorley/database_cleaner,DatabaseCleaner/database_cleaner,yangc5/playlister-sinatra-v-000,yangc5/playlister-sinatra-v-000,yangc5/playlister-sinatra-v-000,awilkening/database_cleaner,glebtv/database_cleaner,ericraio/database_cleaner,HaiTo/database_cleaner