Infer name and version for `luarocks write-rockspec [path]`
Infer name and version for `luarocks write-rockspec [path]`

* Default path for `write-rockspec` is now `.`.
* Use `scm` as default version in all cases.
* Infer rock name as base directory of current path when
  passing `.` as path.

As a result, `luarocks write-rockspec` with no arguments
creates an scm rockspec.

robooo/luarocks,xpol/luarocks,robooo/luarocks,xpol/luainstaller,xpol/luarocks,luarocks/luarocks,keplerproject/luarocks,xpol/luavm,xpol/luainstaller,tarantool/luarocks,keplerproject/luarocks,keplerproject/luarocks,xpol/luavm,robooo/luarocks,tarantool/luarocks,xpol/luarocks,xpol/luainstaller,xpol/luavm,xpol/luavm,luarocks/luarocks,tarantool/luarocks,luarocks/luarocks,xpol/luavm,xpol/luainstaller,xpol/luarocks,robooo/luarocks,keplerproject/luarocks