3.2.2 minor release

New features:

• Add a --dot option for mrc, which outputs a representation of the
  pipeline in GraphViz dot format to standard out.
• In addition to logging the type of filesystem for the pipestance
  directory, also log the type of filesystem for the martian bin
  directory (which is often different from the pipestance directory).
• When stages exceed their memory reservation, mrjob will now log the
  process tree for thet stage, including memory statistics.
• mrp's debug endpoint now exposes the Golang expvar interface in
  addition to pprof.

Other changes:

• Update dependency versions for golang.org/x/sys and some npm
  dependencies.
• Fix the build on OSX (though mrp still does not function there).
• Update vim syntax highlighting to include support for vmem_gb keyword.