Additional tweaks to IO abstraction

[aufdenkampe]

@ptomasula, let us know when you think these are ready to merge back into develop.

[ptomasula]

Thanks @PaulDudaRESPEC & @aufdenkampe
I actually still need to resolve issue #77 before we do the release. Sorry for the delay on that, I'll jump on that this afternoon so that we can wrap this up quickly and hopefully get a release out before the end of the week.

[aufdenkampe]

@ptomasula & @PaulDudaRESPEC, I also have a few items to do before this release:

• Add Doc strings from HSPF descriptions #71 (at least get started)
• HDF5 Class can leave open connections in IPython #83 (update notebooks, as described in this comment)

[ptomasula]

@PaulDudaRESPEC @aufdenkampe
I opened PR #85, which has code that fixes #77. Once that code is merged in, we're good to go on my end.