Segyio

* segyio now reads short attributes from little-endian files correctly

* The from_array function has been refactored, and speed is improved
* create works for non-4-byte numeric formats
* More numerical formats are accepted: 8-byte/64 bit double-precision IEEE
float, 1, 2, and 4-byte signed and unsigned integers
* segyio no longer crashes on key misses in f.gather[int, :]
* The intended TypeError is raised when traces are accessed with None, instead
of a misleading (and wrong) AttributeError
* sample-interval has gotten some new tests
* Minor behavorial improvements to C++ test-config
* Some stack-related bug fixes in the test suite
* The readme has seen some minor updates

* Check endianness variable properly

* Pass HOST_BIG_ENDIAN as preprocessor directive, not compiler option

* Fixed a docstring formatting issue
* Fixed a race condition in test suite

* segyio has learned the seismic unix file format, and can read and write SU
files. This feature is found in the segyio.su module
* segyio supports least-significant-byte (LSB/little-endian) first formatted
files
* Fixed a bug that caused writing headers in non-linear mode very slow,
and wrong under some conditions
* segyio also considers files with descending line/offset numbers sorted, not
just ascending
* The python file handle has learned the interpret method, which allows
specifying structure directly, rather than inferring it from file metadata.
This is particularly useful for files with structure, but broken headers
* A new family of from_array functions are added to the tools module,
intended for quick-and-easy storing a 2/3/4D volume on disk
* Sorting defaults to inline in segyio.create if nothing is specified
* Text.__setitem__ used a wrong variable and didn't really work, but is now
fixed
* Internal imports are tidied up
* The test suite in both Python and C++ have seen some minor improvements
* An experimental C++ interface is available for source builds, but is not
considered stable - internals and interface can change with no prior notice.
The experimental interface is enabled when segyio is built with
-DEXPERIMENTAL=ON