Change parameter names in Google Analytics script

`i` `s` `o` `g` `r` `a` `m` -> `a` `p` `i` `d` `o` `c`

I used [this commit](https://github.com/h5bp/html5-boilerplate/commit/48d49e96d6db282eb9686d31ebbc5cbbbdd4d966) on HTML5 boilerplate as reference.