Format HTML output by default.
 - Can be disabled via environment setting ENV ET_NO_INDENT_MARKUP to 'true'
 - Disabled by default in test_helper so tests don't have to have
   to think about whitespace
 - This disabling can be overridden inside a block passed to
   Tag.formatted
Adjusted performance threshold since recent changes impacted performance
Fix whitespace issue in test
WIP: table_for
Rudimentary table_for works, tests all green