Added option to anonymize IP addresses.

This is done using the anonymizeIP module of Google Analytics. Setting
such option is mandatory in certain countries (e.g. Germany) if you want
to use Google Analytics due to national data privacy laws
Update version number
Added opt-out functionality by means of a cookie

This is also necessary in some countries, e.g. Germany. I have added a
section in the FAQ on how this can be called by a user.

See (in german):
https://www.datenschutzbeauftragter-info.de/fachbeitraege/google-analytics-datenschutzkonform-einsetzen/
http://rechtsanwalt-schwenke.de/google-analytics-rechtssicher-nutzen-anleitung-fuer-webmaster/

See google analytics docs for this is done:
https://developers.google.com/analytics/devguides/collection/gajs/?hl=en#disable
Set transaction currency
change "Add to cart" to "Add to Cart" to make it consistant with line 425
remove the "SKU" prefix to the sku for addItem to make it consistant with what Google Analytics wants for data
put the GA code in the head right at the end of wp_head to get it as close to </head> as possible
Fixes #30
Remove trailing comma after currency declaration
Merge pull request #31 from jnachtigall/master

Add data privacy option that are mandatory in some countries
Merge pull request #33 from ragulka/transaction-currency

Set transaction currency
Merge pull request #35 from matt-h/sku

Remove the "SKU" prefix to the sku for addItem
Merge pull request #34 from matt-h/cart-capital

change "Add to cart" to "Add to Cart" to make it consistent
Merge pull request #36 from matt-h/wp_head

Put the GA code in the head