Data download: keep -1 and -999 flags as integers
Suggest a pretty filename to save data
Now actually return events within time range
Return events over multiple days

This commit contains a full implementation of the datetime range.  Data
spanning multiple days will be returned.
Download: ignore days where data is not available

You can now specify a long timespan and get all available data without a
404.  You also won't get a 404 when no data is available within that
timespan.
Generate CSV output as an iterator for streaming
Disable GZip middleware for now

Django 1.5 implements StreamingHttpResponse to bypass streaming-breaking
middleware.  We should upgrade, but it is not trivial.  For now, disable
GZip to not break streaming.
Bugfix: default 'yesterday' needs to be datetime object
Data download: new 'download' parameter.

If download=True, the Content-Disposition will include 'Attachment;'.
Instead of opening the page and displaying the CSV, the browser will
download a file.
Very basic data download form
Form parameters are passed to download view
Download form: added title
Better content-disposition
Download three days of data
Download data directly from status page

A link from the status page pre-fills the download form.  Thus, it is now
very easy to download data.  Yeah!
Merge branch 'event_summary_data'