Support different config paths (#426)

This makes the configuration files work if neovim's config path is different from `~/.config/nvim`.

lua/lsp/ruby-ls.lua

@@ -1,6 +1,6 @@
 -- If you are using rvm, make sure to change below configuration
 require'lspconfig'.solargraph.setup {
-    cmd = { DATA_PATH .. "~/.rbenv/shims/solargraph", "--stdio" },
+    cmd = { DATA_PATH .. "/lspinstall/ruby/solargraph/solargraph", "--stdio" },
     on_attach = require'lsp'.common_on_attach,
     handlers = {
         ["textDocument/publishDiagnostics"] = vim.lsp.with(vim.lsp.diagnostic.on_publish_diagnostics, {