lazy load lspinstall (#654)

lua/plugins.lua

@@ -34,7 +34,9 @@ return require("packer").startup(function(use)
     -- TODO refactor all of this (for now it works, but yes I know it could be wrapped in a simpler function)
     use {"neovim/nvim-lspconfig"}
     use {"glepnir/lspsaga.nvim"}
-    use {"kabouzeid/nvim-lspinstall"}
+    use {"kabouzeid/nvim-lspinstall", 
+        cmd = "LspInstall",
+    }
     -- Telescope
     use {"nvim-lua/popup.nvim"}
     use {"nvim-lua/plenary.nvim"}