Add HStringTemplate 0.7.3

i686 - https://dl.dropboxusercontent.com/u/58651521/haskell-hstringtemplate-0.7.3-1-i686.pkg.tar.xz
x86_64 - https://dl.dropboxusercontent.com/u/58651521/haskell-hstringtemplate-0.7.3-1-x86_64.pkg.tar.xz