Setting the entire file AST as the node causes golangci-lint to print
the entire file source as the context, and line and column numbers set
to 1. Point to the package name node instead.
Closes#688
This PR introduces a white & black lists of initialisms for the
`var-naming` rule.
Now the rule can be configured with:
```toml
[rule.var-naming]
arguments = [["ID"], ["VM", "BAR"]]
```
This way, the linter will ignore `customId` but will throw on `customVm` or `customBar`.
Fix#41
