gitignore: add debian file
mv lib/osm to osm/
reorganize library

sync.lua, tirex.lua: merge sync.lua into tirex.lua
 - sync.lua depends ngx.sleep so it cannot be
   independent library.

tile.lua:
 - remove ngx.* dependency. now can use on pure Lua.

utils.lua
 - remove ngx.* dependency. now can use on pure lua.
merge to tile.lua

utils.lua:
 - remove and merge tile.lua
   it is definitly tile handling utility.