Reworked ENDF tests to use id form for nuc_i

Additionally, made endf.test_u235 fail with a useful error message
when the data file is missing.
merge conflict fixed
tiny formatting fix
cleaned up tests
fixing import style
Added cython version printing
Merge pull request #191 from scopatz/cyver

Added cython version printing
Merge remote-tracking branch 'upstream/staging' into staging
Made test_endf.test_u235() download missing data if necessary
added u235 to ignore
Fixed ENDF bug where it would not read the data in, now it reads the data in
Merge remote-tracking branch 'upstream/staging' into staging