Explicitly install `bundler 1` in manual installation guide
Explicitly install `bundler 1` in manual installation guide

 #2727

dsander/huginn,virtadpt/huginn,huginn/huginn,gautamkrishnar/huginn,huginn/huginn,eugenesvk/huginn,huginn/huginn,dsander/huginn,virtadpt/huginn,gautamkrishnar/huginn,eugenesvk/huginn,cantino/huginn,cantino/huginn,dsander/huginn,strugee/huginn,gautamkrishnar/huginn,strugee/huginn,virtadpt/huginn,eugenesvk/huginn,cantino/huginn,strugee/huginn