Update README.md

Give compilation instructions to save users time
Merge pull request #158 from TheAncientGoat/patch-1

Update README.md
use a triangle-like distribution for to-hit and damage values
Merge branch 'master' of https://github.com/miki151/keeperrl
one button for digging and cutting trees
add stone to resources
draw a fast and blocking level map view
draw location names and thicker roads on world map
enable world map in keeper mode
fix door deletion crash, add peaceful elves
remove ctags command from makefile
add hotkeys and exit keys to GUI lists
fix bogus doors construction; allow destroying storage; fix pathfinding crash when clicked outisde the level
use the sfml mouse state for right button
use mouse state properly (?)
make the level borders visible
remove ctags from win makefile
add difficulty setting
fix str calculation
possess minion only when in minions tab