New Donor Data Page

This pull request is in response to [Issue #54](https://github.com/undp/undp.github.com/issues/54): Layout for new donor data.  The current donor data page focuses too heavily on donations to non-core funds, such as trust funds and cost sharing.  Our objective was to increase the emphasis on core funding, while still keeping the data on non-core funds.  

We were given a new dataset [core_fund.csv](https://github.com/undp/undp.github.com/blob/donorViz/bin/donor_data/core_fund.csv) describing donations to the UNDP core fund.  We modified the donor data processing script [undp-donors.py](https://github.com/undp/undp.github.com/blob/donorViz/bin/undp-donors.py) to account for the data on core funding.  This script produces a JSON file [donors.json](https://github.com/undp/undp.github.com/blob/donorViz/api/donors/donors.json), which aggregates data about all donors' contributions to each funding modality.

Next we edited the donor view [Donor.js](https://github.com/undp/undp.github.com/blob/donorViz/_includes/views/Donors.js), and its template [donorViz_](https://github.com/undp/undp.github.com/blob/donorViz/_includes/templates/donorViz._) to emphasize the core funding data.  We also kept the table of non-core funds, positioning it below the information on core funds.

Here is a look at the new donor data:

![screen shot 2014-08-27 at 2 23 44 pm](https://cloud.githubusercontent.com/assets/5795460/4065294/674baed0-2e19-11e4-9dbb-d4b6deb83034.png)

Scrolling down the page...

![screen shot 2014-08-27 at 2 24 03 pm](https://cloud.githubusercontent.com/assets/5795460/4065366/ecf52bec-2e19-11e4-91c2-518bce63d9f7.png)