+ README in main directory

README

+Minetest Δ (“Minetest Delta”) is a fork of Minetest-c55 <http://celeron.55.lt/~celeron55/minetest/>, incorporating experimental features that are not (yet) included in Minetest-c55.
+
+New bricks:
+* Sandstone (crafted from 4 sand)
+
+Alternate graphics:
+* Player
+* Omsk birds (instead of Oerkki ghosts)
+* Rat
+* Glass
+
+Building on GNU/Linux:
+    cmake . -DRUN_IN_PLACE=1
+    make -j2