v0.4 summary issue

[rtimms]

Roadmap issues:

• blended electrodes Feature request: support for blended electrodes #23
• validation based on models Validation based on models #29
• "additional" parameters Allow "miscellaneous" category #26
• split validity from completeness Separate out validity from completeness  #40
• extra examples to show off hysteresis (via additional parameters) and blended electrodes
• API docs
• user guide
• change a_n and a_p to b_n and b_p (the surface area per unit volume) in eq. (6c) in the BPX document -- a small bug fix

Extras:

• active material volume specification Simplify specification of active material content #41

[ejfdickinson]

As discussed earlier, I agree with the suggestion to delay #40 to a future release.