FIX: Add endianness missing flag when reading data
Added endianess flat to data type to allow data to be read cross platforms

closes #8688

@yarikoptic @jreback I think this one is ready.
 @yarikoptic ok on these platforms?
 @bashtage IIRC the tests are disabled on non-small so is this actually tested?
 All of the tests were re-enabled for big-endian a few releases ago.

There are only three tests that are skipped on any platform:

https://github.com/pydata/pandas/blob/master/pandas/io/tests/test_stata.py#L256

I would like to kill these in a different PR since they rely on proprietary data and so will never be re-enabled.
 ok, ping on green
 @jreback It is ready.
 thanks!
