For lineNumber use getCursorBufferPosition()

When using getCursorScreenPosition() with soft wrap the line number is
incorrect and the location in the document is incorrect. Instead use
getCursorBufferPosition() which does not count wrapped lines.
For further details see
https://atom.io/docs/api/v0.187.0/TextEditor#buffer-vs-screen-coordinates

Closes #68

lib/composer.coffee

@@ -148,7 +148,7 @@ class Composer
 
     editorDetails =
       filePath: editor.getPath()
-      lineNumber: editor.getCursorScreenPosition().row + 1
+      lineNumber: editor.getCursorBufferPosition().row + 1
 
   alterParentPath: (targetPath, originalPath) ->
     targetDir = path.dirname(targetPath)