Templating languages: bundle just the runtime; fixes #15

[danburzo]

Adds the tip as discussed in #15.

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[danburzo]

(I've also signed the Google CLA.)

[googlebot]

CLAs look good, thanks!

[iamakulov]

Thanks a lot for the PR! I took the liberty to split your text into two parts (one for handlebars, and one for ractive, to simplify finding matching libraries for repo visitors).

I also omitted Vue since, it seems, using vue-loader is just the default approach for Vue developers? (I’m not a Vue dev though so please correct me if I’m wrong!)