use print_function, head off other 2.7->3.4 issues
clean up test droppings
Style changes

SCFcache is slightly more understandable now
remove redundant import
reraise "wrong" errors in test function
verbose display cleanup, more style changes
Merge branch 'master' into idea-polymer-updates
SZdist refactor
Inner loop optimizations

Surprising speedup from combining array and pointer access. The inner
loop is less of a bottleneck lately though so overall gains are minimal.
python 2->3 tweaks for polymer code

tested on 2.7.6 and 3.4.2 (i.e. polymer_test.py finishes)
Merge pull request #62 from richardsheridan/idea-polymer-updates

print function and test changes, as suggested