php 7 compatibility

Found a compatibility issue to address.
I moved my site from Ubuntu 14 to Ubuntu 16.04, which uses php7.

php7 does not include mbstring by default.

Since I am running my site on a private server, I was able to run this:
apt-get install php-mbstring php7.0-mbstring php-gettext libapache2-mod-php7.0

However, if the server was hosted, this may not have been possible.

You may want to consider re-writing index.php on line 23, as it throws a fatal error.

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