[Fix #623] Restored kill-region defadvice

When no region selected `C-w` kills current line
[Close #547] Removed ack-and-a-half from prelude
Merge pull request #762 from k1-hedayati/remove-ack

[Close #547] Removed ack-and-a-half from prelude
Merge pull request #761 from k1-hedayati/restore-kill-region-defadvice

[Fix #623] Restored kill-region defadvice
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