add a package argument to help_console

This allows the `help_console` function to work when two loaded namespaces both contain an identically named exported object, by passing a package name to `utils::help`. The reason for the package value to be written as `(package)` inside `help` is due to non-standard evaluation of the `package` argument (see examples in `? help`). For context and motivation, see [this post on StackOverflow](http://stackoverflow.com/questions/26804298/getting-help-of-r-function-using-help-console-function-from-noamtools-r-package).