Merge pull request #34 from TheTracyL/master

New building, store and album Dashicons. Props @TheTracyL
Adding 4.0 icons

dashicons-calendar-alt, dashicons-grid-view, dashicons-index-card, and
dashicons-carrot.

Added dashicons-building, dashicons-store, and dashicons-album for an
upcoming point release.
Redirecting demo page to developer.wp.org

Since we have a shiny new Dashicons demo page that now lives somewhere
official.
Update README.md
new dashicons

f515 repeat, f516 skip_back, f517 skip_forward, f518 back, f519
forward, f520 volume_off, f521 volume_on, f522 play, f523 pause, f524
tickets, f525 phone, f526 money, f527 palm_tree, f528 image_left, f529
image_center, f530 image_right, f531 image_block
Adding css selectors for new Dashicons: f515 repeat, f516 skip_back, f517 skip_forward, f518 back, f519 forward, f520 volume_off, f521 volume_on, f522 play, f523 pause, f524
tickets, f525 phone, f526 money and f527 palm_tree