Replace rockspecs/ with a single scm rockspec (#108)

There is no need to keep rockspecs for older versions - it's enough
to ensure that `luarocks make` builds currently checked out version.

`luarocks new-version <rockspec> <version> --tag=<tag>` generates
rockspecs for releases.

Use `scm` instead of `dev` as LuaRocks 2 thinks that `dev` versions
are less than normal versions like 1.6.3, making it tricky to
use bleeding-edge version as a dependency with a constraint
such as `luafilesystem >= 1.6.3`.

luafilesystem-scm-1.rockspec

@@ -0,0 +1,28 @@
+package = "luafilesystem"
+version = "scm-1"
+source = {
+   url = "git://github.com/keplerproject/luafilesystem"
+}
+description = {
+   summary = "File System Library for the Lua Programming Language",
+   detailed = [[
+      LuaFileSystem is a Lua library developed to complement the set of
+      functions related to file systems offered by the standard Lua
+      distribution. LuaFileSystem offers a portable way to access the
+      underlying directory structure and file attributes.
+   ]],
+   license = "MIT/X11"
+}
+dependencies = {
+   "lua >= 5.1"
+}
+build = {
+   type = "builtin",
+   modules = {
+      lfs = "src/lfs.c"
+   },
+   copy_directories = {
+      "doc",
+      "tests"
+   }
+}