FIX version number autocomplete sort order should be numeric

[allanlaal]

currently its alphabetic:

  allan@L4:~$ phpenv install 7.1
  7.1.0        7.1.25
  7.1.1        7.1.26
  7.1.10       7.1.27
  7.1.11       7.1.28
  7.1.12       7.1.29
  7.1.13       7.1.3
  7.1.14       7.1.30
  7.1.15       7.1.31
  7.1.16       7.1.32
  7.1.17       7.1.33
  7.1.18       7.1.4
  7.1.19       7.1.5
  7.1.2        7.1.6
  7.1.20       7.1.7
  7.1.21       7.1.8
  7.1.22       7.1.9
  7.1.23       7.1snapshot
  7.1.24