reorganize code

lua/lib/conf.lua

@@ -0,0 +1,23 @@
+local BUF_NAME = 'LuaTree'
+local function get_cwd() return vim.loop.cwd() end
+local ROOT_PATH = get_cwd() .. '/'
+
+local function get_buf_name()
+    return BUF_NAME
+end
+
+local function get_root_path()
+    return ROOT_PATH
+end
+
+local function set_root_path(path)
+    ROOT_PATH = path
+end
+
+return {
+    get_buf_name = get_buf_name;
+    get_root_path = get_root_path;
+    set_root_path = set_root_path;
+    get_cwd = get_cwd;
+}
+