set default-directory in dwarf-browse

set default-directory in dwarf-browse

I've been using dwarf-mode.el again recently and I found it mildly
annoying that the mode doesn't set default-directory.  Setting it
means that operations in the dwarf-browsing buffer default to the
directory holding the object file being investigated.

This bumps the version number as well so that updating it via the
package manager works properly.

2016-11-04  Tom Tromey  <tom@tromey.com>

	* dwarf-mode.el (dwarf-browse): Set default-directory.  Bump
	version number.