Dont auto generate last build date

[msathis]

I'm not sure whether this is useful for others. In our case we were checking E-Tag header to figure out any feed change. Because this lastBuildDate is auto generated, the E-Tag was always changing though no feed item got changed.

[Mithgol]

It seems that the tests should also be changed to pass.

[alexjorgef]

Linter failed to run due to warnings, if statement should have curly braces.

    if (data.lastBuildDate) {
        channel.push({ lastBuildDate:  data.lastBuildDate });
    }