Add option to configure the linters by YAML

:memo: Adds the option to configure suspiciouss with a `.suspicious` file listing the linters to include and/or exclude.
:warning: Without a `.suspiciouss` file in the root folder all the current linters would still be used when suspiciouss is run.

The idea behind this is that you can write additional linters that can be excluded if they are not required. For example, if you are using [BEM](http://bem.info/) syntax you could write a linter that parsed the CSS to enforce the correct usage of BEM syntax. Or, you could write a linter the discouraged the usage of `em` units. Those additional linters - or indeed existing linters - can then be added/removed as required.

_The above linters may, or may not, be part of future PRs_ :grinning: