Running `bundle update --bundler` on a rails app locally:
```
==> memprof.after.txt <==
Total allocated: 301.90 kB (3794 objects)
Total retained: 73.24 kB (698 objects)
==> memprof.before.txt <==
Total allocated: 14.47 MB (196378 objects)
Total retained: 25.93 kB (202 objects)
```
So for a slight increase in retained memory (all keys are now retained),
we go from about 200k allocations in the settings file to under 4k
e64debb6ae
