Revert a hack that blocks scope flexibility

Hardcoding the scope disables the settings that are defined in the application itself, and blocks per-implementation scope configuration.
The scope can be defined when creating/updating a LinkedIn app, so it's useless to hack it.
The scope should be hardcoded only if it can be set elsewhere, out of the library, so that implementation can define their own scope directly, so not as a constant.
Application scope setting seems the most flexible solution for the moment.
Merge pull request #146 from Facyla/patch-1

Revert a hack that blocks scope flexibility - LinkedIn provider