Most analytics software do provide users with plugins to insert code into themes, but why use plugins to insert simple HTML code into your theme? I have been using a very useful plugin called Footer Stuff (WP repo link) which allows me to add code to the header and the footer of the site without having to manually edit the theme.
The best part of the plugin though is the fact that it will insert the code into the theme no matter how often I change the theme without having to constantly edit the theme.
Footer Stuff Walkthrough
Head over to the plugins page in your admin dashboard and do a quick search for footer stuff, install and activate the plugin and you are ready to add code to your theme.
An option to personalize footer stuff is present under Appearance. Clicking on the Footer Stuff link will display a HTML form containing two text boxes. The box on the top is to add content to your footer, and the second one is to add content to your header.
Once you add the code you want, footer stuff will automatically insert it into your theme, no matter which one you use. However, your theme needs to make use of the functions wp_head() and wp_footer(), without which the plugin won’t work.
Overall I found the plugin to be very useful. Also considering that many people do not have the skills to edit HTML and PHP files, they can do away with several plugins by using this plugin, all you have to do is copy the code from the source and then add it to footer stuff.
Have you used this plugin before? If not, will you use it to simplify theme edits? Do let me know.