Respect initialLine and initialColumn options when reopening a file

Fix #1743
Remove unused variable and extra newline from text-editor-spec
Call setCursorBufferPosition only if this method exists

@kevinsawicki:
That way in the case where a custom editor is opened that isn't a text editor,
it won't blow up if the custom editor doesn't implement setCursorBufferPosition.
Remove unused variable from text-editor-spec
Merge pull request #4729 from alexandershov/master

Respect initialLine and initialColumn options when reopening a file