[SPARK-2951] [PySpark] support unpickle array.array for Python 2.6

Pyrolite can not unpickle array.array which pickled by Python 2.6, this patch fix it by extend Pyrolite.

There is a bug in Pyrolite when unpickle array of float/double, this patch workaround it by reverse the endianness for float/double. This workaround should be removed after Pyrolite have a new release to fix this issue.

I had send an PR to Pyrolite to fix it:  https://github.com/irmen/Pyrolite/pull/11

Author: Davies Liu <davies.liu@gmail.com>

Closes #2365 from davies/pickle and squashes the following commits:

f44f771 [Davies Liu] enable tests about array
3908f5c [Davies Liu] Merge branch 'master' into pickle
c77c87b [Davies Liu] cleanup debugging code
60e4e2f [Davies Liu] support unpickle array.array for Python 2.6
[SPARK-1087] Move python traceback utilities into new traceback_utils.py file.

Also made some cosmetic cleanups.

Author: Aaron Staple <aaron.staple@gmail.com>

Closes #2385 from staple/SPARK-1087 and squashes the following commits:

7b3bb13 [Aaron Staple] Address review comments, cosmetic cleanups.
10ba6e1 [Aaron Staple] [SPARK-1087] Move python traceback utilities into new traceback_utils.py file.