Adds utility script to prepopulate cache (closes #28).

[chuckharmston]

• Remove coverage from run.sh
• Test for recommendation.tasks.task_recommend.make_key
• Test for prepopulate.explode
• Test for prepopulate.queue
• Test for prepopulate.wikipedia
• Test for prepopulate.alexa

[chuckharmston]

This is pretty neat, though.

[coveralls]

Coverage remained the same at 100.0% when pulling 2ac4cbb on chuckharmston:28-prepopulate into 5a0c1ff on mozilla:master.

[chuckharmston]

No longer WIP!

r? @6a68

[jaredhirsch]

@chuckharmston Looks good to me overall, tests passing for me locally.

Any reason we aren't using the Alexa US top 1000? We're just targeting en-US for the initial release.

Needs a rebase, then feel free to merge.

[coveralls]

Coverage remained the same at 100.0% when pulling 7330bdd on chuckharmston:28-prepopulate into 6af094b on mozilla:master.

[chuckharmston]

I used what @nchapman suggested in the bug; easy to tweak. I'd file a followup bug, but in a quick search I couldn't find any US-specific raw data sources.