arrow

ARROW-222: Prototyping an IO interface for Arrow, with initial HDFS target

- Switch Travis CI back to Ubuntu trusty (old Boost in precise has issues with
  C++11)
- Adapt SFrame libhdfs shim for arrow
- Create C++ public API within arrow:io to libhdfs
- Implement and test many functions in libhdfs
- Start Cython wrapper interface to arrow_io. Begin Python file-like interface,
  unit tests
- Add thirdparty hdfs.h so builds are possible without a local Hadoop distro
  (e.g. in Travis CI).

Change-Id: I4a46e50f6c1c22787baa3749d8a542216341e630