Replace text in recursively found files

1. M-x find-name-dired: you will be prompted for a root directory and a filename pattern.
2. Press t to “toggle mark” for all files found.
3. Press Q for “Query-Replace in Files…”: you will be prompted for query/substitution regexps.
4. Proceed as with query-replace-regexp: SPACE to replace and move to next match, n to skip a match, etc.

Based on: http://stackoverflow.com/questions/270930/using-emacs-to-recursively-find-and-replace-in-text-files-not-already-open