npm_installer: Skip creating package.json

If the package name in the `package.json` file generated by `npm
init` matched the name of one of the packages to be installed, npm
would error out. It turns out that npm will happily install packages
without the current directory containing a `package.json`, so just
do that instead of any gymnastics to avoid name the name collision.

fixes #409

lua/lspconfig/util.lua

@@ -392,8 +392,7 @@ function M.npm_installer(config)
     set -e
     mkdir -p "{{install_dir}}"
     cd "{{install_dir}}"
-    [ ! -f package.json ] && npm init -y
-    npm install {{packages}} --no-package-lock --no-save --production
+    npm install {{packages}} --no-package-lock --no-save --no-color --no-progress
     {{post_install_script}}
     ]]):gsub("{{(%S+)}}", install_params)
     cmd:write(install_script)