php55-mustache: convert from sha1 to sha256
php55-mustache: convert from sha1 to sha256

Closes #2267.

Signed-off-by: Andy Blyler <e3579b1e47f273529f0f929453e939a68ede9fd1@blyler.cc>

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