Parse line numbers for ember-template-lint

## Information

**VIM version**

VIM - Vi IMproved 8.0 (2016 Sep 12, compiled Nov 28 2017 06:16:39)
macOS version

Operating System: MacOS 10.13.2

## What went wrong

ember-template-lint doesn't put the sign on the correct line number in SignColumn; the sign is just on line 1.

## Reproducing the bug

Steps for repeating the bug:

1. Write a handlebars file with an error or warning in it
2. See that the error/warning sign is only on line 1