Run all linters per package. It allows unloading package data when it's processed. It dramatically reduces memory (and CPU because of GC) usage. Relates: #337
This commit adds full support for bodyclose linter (https://github.com/timakin/bodyclose), which checks if an `http.Body` element is correctly closed after usage. Since it can be used via `go/analysis', I followed the `govet' example as suggested by https://github.com/golangci/golangci-lint/wiki/How-to-add-a-custom-linter. This commit is fully tested, and contains a (flawed) test program which calls `http.Get()' on `https://google.com' and does not closes its corresponding `http.Body'.
