Fixed mentions of `melpa.el`

Signed-off-by: Arne Jørgensen <arne@arnested.dk>
Merge pull request #1541 from arnested/package-filter-doc

Fixed mentions of `melpa.el`
Merge pull request #1542 from kawabata/master

New receipes for 'nnir-est', Gnus nnir interface for HyperEstraier.