Adds php55-libsodium
Adds php55-libsodium

Closes #1696.

Signed-off-by: Alan Ivey <ee249fd9166eccef852f50ca0cbb6ff8665afe99@gmail.com>

mkalkbrenner/homebrew-php,philcook/homebrew-php,dguyon/homebrew-php,TomK/homebrew-php,ablyler/homebrew-php