Avoid keeping track of two lists of nodes during parsing.
Use super rather than render_all in single block render classes.
Merge pull request #445 from Shopify/prefer-super-over-render-all

Use super rather than render_all in single block render classes.
Merge pull request #444 from Shopify/remove-block-children

Avoid keeping track of two lists of nodes during parsing.
Fix flaky test which assumes total_render_time can't be 0.

jruby has millisecond precision for Time.now, so total_render_time can be 0
due to this lack of precision.
Merge pull request #449 from Shopify/fix-flaky-total-render-time-test

Fix flaky test which assumes total_render_time can't be 0.
Remove Liquid::FilterNotFoundError since it is never raised.
Merge pull request #448 from Shopify/remove-unused-filter-not-found-error

Remove Liquid::FilterNotFoundError since it is never raised.
Check and handle when a tainted variable is used
Auto-untaint variables passed through 'escape'
Add tainting tests
Address code review comments

- clean up comment wording
- fix potentially leaky tests