better error handling, adding ENDFDataSource.reaction that uses rxname to accept all rx
discretized tweaks, api improvement
Merge remote-tracking branch 'upstream/staging' into staging
Reinstated import guards
Remove unused imports

Use pylint to find unused imports and remove them.
fixed conflict in import merge
This makes pictures but has Physics Problems
moving discretize back into ENDFDataSource
Merge remote-tracking branch 'upstream/staging' into staging
ENDF discretization should work, actually, for real, this time.
changing Eint to e_int because lowercase, adding slight docs
slight commenting
PEP8
docfix
Added missing 'np.' to 'e'
Update ENSDF data and add small fix on ensdf.half_life.
made some import paths relative.
Merge pull request #213 from scopatz/relpaths

Relative Import Paths