Add a few improvements to the abstract suggested by Arif Merchant to
make it more self contained.  After the first sentence explains that
pipelines of applications need to communicate with each other, briefly
describe the problem with common solutions such as CSV files in a new
sentence, before transitioning to the third sentence to talk about
protocol buffers.  Then after this, uncomment Jeroen's sentence from
elsewhere in the paper which I had moved here which describes how they
offer a unique combination of ...

After this change, section 2 starts at the top of page 3 instead of
the last line of page 2, which is a nice change in the layout.



git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rprotobuf@843 edb9625f-4e0d-4859-8d74-9fd3b1da38cb