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
Regression test for including assignments
Merge pull request #450 from Shopify/additional_test_for_includes

Regression test for including assignments
Merge pull request #440 from Shopify/drop-tainting

Variable tainting
Avoid modifying the default resources limits hash.
Merge pull request #453 from Shopify/no-modify-default-resource-limit

Avoid modifying the default resources limits hash.
Line numbers for all parse errors
Test line number of errors in nested blocks.
Merge pull request #455 from Shopify/parse_error_line_numbers

Line numbers for all parse errors
Parse expressions in Liquid::Variable#parse.