Add feature to permanently ignore files based on a scope

Talisman now supports permanently ignoring certain files using an idea called scopes.
A scope defines a set of files that will be ignored by talisman during scans.
There a currently a few hard-coded set of scopes (node, go to support nodeJS and Go-lang respectively). Users cannot create their own scopes.
A guideline for adding scopes vi github Pull Request's is being prepared.