Ensure the file exists before requiring
Ensure the file exists before requiring

This will avoid rubygems trying to activate a gem containing the path,
which in a few commits time will make spring faster.

maclover7/spring,oggy/spring,grosser/spring,ypresto/spring,slobodankovacevic/spring,pigoz/spring,universsky/spring-1,y-yagi/spring,oggy/spring,smathy/spring,mariusbutuc/spring,rails/spring