added new syntax for comments

comments can now be inserted into liquid variables using the following syntax.

{* this is a comment *}
added support for multi-line comments using the new syntax
added new comment style to history
allow newlines just after {% and {{, as well as just before %} and }}
added tests for new multiline tags
fixed multiline inside a tag, i.e. {% assign foo\n=\n'bar' %}

added tests to verify
added changes to history
Merge branch 'dev-multiline'
Merge branch 'dev-new-comments'

Conflicts:
	History.md
	lib/liquid.rb
	lib/liquid/block.rb