Search index loads very slow on firefox

[isaisabel]

As a user of the ATT&CK website, I want to be able to use my favorite browser without negative impacts to the performance and functionality of the site.

The search index takes much longer to load or parse than on comparable browsers (chrome). In testing, firefox finishes loading/parsing in 20 seconds while chrome takes just 4.

The networking panel indicates that the ajax requests take a similar time (400ms) in both browsers so this may be a browser inefficiency in the parsing or handling of the index data. Further diagnosis is necessary.

[isaisabel]

See also #167