Conflicts:
	setup.py
	topydo/Commands.py

Remove priorities from multiple todo items at once

+ Test new multi-todo functionality.
+ Change name of tests from set_prio to depri

Yes, I'm too tired for this. :/

Guess I'm too tired for this.

Add tests for EditCommand

Edit the archive file with '-d' option.

Split the CLI class into a CLI base class.

This implements archive option from #2.

Implementation of editing todos in $EDITOR

implements #2

- `topydo edit` will still open todofile in $EDITOR
- `topydo edit 1 2 3` will open tmpfile with corresponding todos
- `topydo edit -e @Home due:today` will open tmpfile with todos matching
   the expression

This is done by applying the colors as the last step, so the preceding
filters don't have to worry about it.

Introduce MultiCommand class for cmds operating on multiple todos.