Added a check to 'vaspio.py' testing that the number of columns
implies that the Fermi weights are present in EIGENVAL. This check ensures
that the new format (starting from VASP 5.4) of the file is used.
Corresponding test is added to the suite.
Added 'rpath.py' module to determine the current directory.
Also fixed the test example for EIGENVAL: VASP 5.4 uses a format
with Fermi weights output (unlike previous versions).
Originally, the tests worked only when run from their respective
directory. If one tries to run them from another directory (which happens
when test discovery is used) the tests were not able to find the input files.
Now, a dummy module 'rpath' is added to all tests whose sole role is
to obtain the current path.
The files from the original vasp-interface repository are reshuffled in
accord with the directory structure of dft_tools. Some of the directories,
such as 'test' (unit tests for the interface), 'examples' (simple examples for
the development purposes) are temporarily placed into 'python/vasp' directory
to avoid confusion with integral tests and examples of dft_tools.
