modern browsers eat first newline in textarea.

Modern browsers eat first empty line in textarea block.
see https://code.djangoproject.com/ticket/8627

so when we parse form, we need to remove leading newline char in textarea block.

My tests broken after I started to migrate to django 1.5 branch, I use webtest to functional testing.

Also please note, that it only affects html.parser beautufulsoup builder. because in html5lib leading newline removed automaticly https://github.com/html5lib/html5lib-python/blob/master/html5lib/html5parser.py#L993.