Update Porter to use latest `nucypher` changes for dkg-dev-6

[derekpierre]

Candidate for Porter dkg-dev-6.

Modifications based on latest nucypher changes for dkg-dev-6:

• Learner no longer stores eth_provider_uri
• Conditions are now versioned and use prefix notation (does not affect Porter but does affect testing).

[KPrasch]

LGTM!

[codecov-commenter]

Codecov Report

Merging #29 (b23bf27) into development (a97468a) will increase coverage by 0.01%. The diff coverage is 100.00%.

@@               Coverage Diff               @@
##           development      #29      +/-   ##
===============================================
+ Coverage        87.84%   87.85%   +0.01%     
===============================================
  Files               18       18              
  Lines              732      733       +1     
===============================================
+ Hits               643      644       +1     
  Misses              89       89              

Impacted Files	Coverage Δ
porter/main.py	87.21% <100.00%> (+0.09%)	:arrow_up: