Get the module for the current line of a file about elixir_sense

[lukaszsamson]

I believe with the changes from #234 the need for that is lower.
The problem with our approach is that we use token_metadata from AST. This works well for standard elixir code but it will fail for anything macro generated. In elixir a code position moay correspond to many modules. There's no better standard lib API that returns code ranges for module as of 1.15. Compile tracer only returns begin line in macro env. Docs return begin line and column.