BLD : actually install the extern folder

 - minor PEP8
 - add pims.extern to the package list
fix example notebook a bit so that it works with current pims
Merge pull request #73 from triplepoint217/master

fix example notebook a bit so that it works with current pims
BUG : made Frame respect creation time metadata

Frame(data, frame_no=frame_no, metadata=md_dict) dropped
md_dict.

 - Added test
 - minor style changes
Merge pull request #76 from danielballan/fix-metadata

TST/FIX: Implement metadata in Frame and add test
Merge pull request #69 from tacaswell/install_extern

BLD : actually install the extern folder