Remove Gollum::FileView

[benjaminwil]

It appears this file is never used anywhere by gollum or gollum-lib. So we can safely remove it.

I manually verified that removing this breaks nothing:

• I manually visited all Gollum pages.
• I manually deleted a page and ensured that there was still a confirmation dialog.
• I ran the gollum test suite.
• I ran the gollum-lib test suite.

If you can think of anything else we should do to verify this change let me know. But it really seems like this is just dead code.

[dometto]

Good find!