ENH: allow file pattern at first position
DOC: more extensive description
RF+SML: indent
DOC+ACK: provide examples of loading data. Added example of loading multiple beta images as suggested by #Reshanne R. Reeder#
DOC: more examples
OPT+SML: minor optimization
RF+NF: use persistent variable to keep track of which externals were used + provide list of citation information
NF: add citation information to demos
RF+ENH+EXP+ACK: attempt to better deal with nifti files with flip_orient and rot_orient. this feature is experimental. thanks to #Jens Scharzbach# for providing a nifti file for testing