Updating README with download/git information.

The git instructions were hard to find and this way they will show up
on github.
Merge remote-tracking branch 'origin/fastpath'

* origin/fastpath:
  Add curl to list of optional dependencies
  Update test and baseline for a recent doc test fix
Next version of the threading queue deadlock fix.

We now just use the read/write counters, as suggested by Gilbert.
Merge remote-tracking branch 'origin/fastpath'

* origin/fastpath:
  Revert "Fix the dir module."
  Fix the dir module.
Updating submodule(s).

 [nomail]
Merge branch 'master' into fastpath
Fix race condition in unit test.

Removing an input stream immediately after it's created causes a race
to read the entire file before the reader gets the signal to stop.