Optional line numbers for liquid errors
Remove parser switching duplication
Add line numbers to warnings
put line number in parentheses
Clean up Liquid::Error#render
remove unnecessary method
prefix for Liquid::Error instances
remove unnecessary nil
move line number check
merge conflicts
Revert "move line number check"

This reverts commit 939365c234e00152a2cbc8c4b5d711638bfba13a.

Conflicts:
	lib/liquid/template.rb
Fix JRuby builds
Merge pull request #419 from Shopify/liquid_error_line_numbers

Optional line numbers for liquid errors