Version 1.3.4

Changelog:

• Reading a slice in gather mode is significantly faster
• Use ftello when available to support large files on systems where long is 32-bit
• The python extension is changed to use C++; a C++ compiler is now required,
  not just optional, when building the python extension
• Many internal and infrastructure improvements
• The python library is built with setuptools - still integrated with cmake.
  Users building from source can still do cmake && make
• Git tag is now authority on version numbers, as opposed to the version string
  recorded in the cmake file.
• General building and infrastructure improvements