Relax HAML dependency
Relax HAML dependency

The HAML dependency was very specific, which resulted in problems when
this gem was included alongside gems such as `html2haml`.

While the intent of pinning at this specific version was originally to
mitigate problems due to potential monkey patching, this didn't end up
being a requirement.

Relax the dependency to require HAML 4.0+.

Change-Id: Ie5281f2eb9f52fb65ae52d229823238865fc83ff
Reviewed-on: https://gerrit.causes.com/33567
Tested-by: jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@causes.com>
Reviewed-by: Shane da Silva <6f6e68d1df92f30cb4b3ce35260ddf94a402f33d@causes.com>

mzp/haml-lint,skateman/haml-lint