missing data in production

The `Download.counts_by_day_for_version_in_date_range` method looks in redis to see if the download history is there (https://github.com/rubygems/rubygems.org/blob/master/app/models/download.rb#L79-L107 is the method in question at time of this writing). 

The test is putting data in redis and confirming the count returned by that method is correct. The test and method do work, so all is well. However, failing redis data, it falls back to searching VersionHistory records. Unfortunately, it looks like there are missing VersionHistory records in rubygems.org's production data. 

Example: `rails-2.3.5`.

Looking at https://rubygems.org/gems/rails/versions/2.3.5 it says the total download count for that version is aprox ~1M downloads. However, the api is returning a download count of 33k. Pretty weak comparison. The redis data is probably missing old data, and there no VersionHistory records in the database dump either. The dump is attached to this post on this branch. 

Console with the dump:

<pre>
1.9.3p0 :005 > VersionHistory.count
 => 350364
1.9.3p0 :004 > VersionHistory.last.day
 => Tue, 07 Aug 2012
</pre>

But none for rails:

<pre>
1.9.3p0 :013 > version.id
 => 113389
1.9.3p0 :014 > version.rubygem.name
 => "rails"
1.9.3p0 :015 > version.number
 => "2.3.5"
1.9.3p0 :016 > VersionHistory.where(:version_id => v.id)
 => []
</pre>

I don't have the redis dump, but given the data coming back from that method, it seems redis has missing data as well.

It looks like redis does have some download info on this gem, but only from march this year. The data coming back from the api (should be a sum of 1M but is only ~33k) returns 0's all the way from 26th of November until the 8th of March 4 years later. 

<pre>
1.9.3p0 :017 > Gems.downloads('rails','2.3.5',5.year.ago, Time.now)

# data returned starts way after the gem was actually built
# ["2009-11-26", 0]...["2013-03-07", 0], ["2013-03-08", 178]
</pre>
Some more inconsistencies: https://gist.github.com/shaiguitar/d2af997b7f58e24fd305