Update default version of require.js

[kasium]

It seems like that the default version of require.js hardcoded in the plugins source code leads to some issues, see #678 and SAP/swagger-plugin-for-sphinx#343. For me it helped to update the version to 2.3.7 (latest one). While its possible to do this via the configuration, it would be great if you could update the default

[mgeier]

Thanks for reporting this!

I don't see any reason not to update the default ... would you like to make a PR?

[kasium]

sure, let me open one