When a file is downloaded, make it executable.

Updates to docs (including nav structure)

- Rework/expand the nav bar with more of the docs site
- Removing parts of docs about EC2 and Mesos that differentiate between
  running 0.5 and before
    - Merged subheadings from running-on-amazon-ec2.html that are still relevant
      (i.e., "Using a newer version of Spark" and "Accessing Data in S3") into
      ec2-scripts.html and deleted running-on-amazon-ec2.html
- Added some TODO comments to a few docs
- Updated the blurb about AMP Camp
- Renamed programming-guide to spark-programming-guide
- Fixing typos/etc. in Standalone Spark doc

Updates to docs

which generates scala doc by calling `sbt/sbt doc`, copies it over
to docs, and updates the links from the api webpage to now point to
the copied over scaladoc (making the _site directory easy to just
copy over to a public website).

but removed the collapsable stuff from the nav bar.

responsive css (so nav menu doesn't switch to collapsed version
for narrow viewports).

YARN and standalone documentation

to use pygments syntax highlighting.

git weirdness).

Fix links and make things a bit prettier.

easier to read.

Adds a "docs" directory containing existing Spark documentation and doc build instructions

docs/README.md to describe use of Jekyll, and renmaed things to make them
more consistent with the lower-case-with-hyphens convention.

which can be compiled via jekyll, using the command `jekyll`. To compile
and run a local webserver to serve the doc as a website, run
`jekyll --server`.

Spark HTTP FileServer

Conflicts:
	core/src/main/scala/spark/SparkContext.scala