Add basic infrastructure for unit testing

Tests will be written using the [moonscript](http://moonscript.org/) language,
a lua 'dialect' that is whitespace-significant and has a syntax similar to
coffeescript. The test framework used is [busted](http://olivinelabs.com/busted/),
a bdd framework for lua/moonscript.

Luajit has a nice ffi module, which lets lua programs link shared libraries and
call it's functions without writing any C code.

To take advantage of this fact for testing C functions, a new target was added
to CMakeLists.txt, which compiles neovim as a shared library that is loaded by
the process running the tests.

This commit adds necessary code for downloading and installing a lua package
manager(luarocks) locally. It wasn't added as a subtree because there are quite
a few blobs in its source tree.

scripts/compile-lua.sh

@@ -0,0 +1,6 @@
+. scripts/common.sh
+
+lua_dir="$pkgroot/third-party/luajit"
+
+cd "$lua_dir"
+make PREFIX="$prefix" install

scripts/setup-test-tools.sh

@@ -0,0 +1,22 @@
+. scripts/common.sh
+
+luarocks_ver=v2.1.2
+luarocks_repo=keplerproject/luarocks
+luarocks_sha1=69ea9b641a5066b1f316847494d8c63a4693977d
+luarocks_dir="$pkgroot/third-party/luarocks"
+
+github_download "$luarocks_repo" "$luarocks_ver" "$luarocks_dir" \
+	"$luarocks_sha1"
+
+cd "$luarocks_dir"
+
+./configure --prefix="$prefix" --force-config --with-lua="$prefix" \
+	--with-lua-include="$prefix/include/luajit-2.0" \
+	--lua-suffix="jit"
+
+make bootstrap
+
+# install tools for testing
+luarocks install moonrocks --server=http://rocks.moonscript.org
+moonrocks install moonscript
+moonrocks install busted

scripts/unittest.sh

@@ -0,0 +1,6 @@
+. scripts/common.sh
+
+(cd "$pkgroot/build" && make) || exit 1
+eval "$(luarocks path)"
+
+busted --pattern=.moon ./test