Replacing NERDTree with Ctrl-P

For many months, I used NERDTree to view my project directory within Vim. During my introduction to Rails application development, it was valuable to see the Rails tree structure in my left sidebar. Two weeks ago, I un-installed NERDTree from my .vimrc because I realized that I could improve my workflow without it. I used to depend so much on NERDTree. With NERDTree, the visual tree structure fixe