Add separate RPC for contract code

[keefertaylor]

No description provided.

[codecov]

Codecov Report

Merging #73 into master will increase coverage by 0.32%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master      #73      +/-   ##
==========================================
+ Coverage   42.89%   43.21%   +0.32%     
==========================================
  Files          57       58       +1     
  Lines        1140     1187      +47     
==========================================
+ Hits          489      513      +24     
- Misses        651      674      +23

Impacted Files	Coverage Δ
TezosKit/RPC/GetAddressCodeRPC.swift	0% <ø> (ø)	⬆️
...ResponseAdapters/ContractCodeResponseAdapter.swift	0% <ø> (ø)	⬆️
TezosKit/Conseil/GetOriginatedAccountsRPC.swift	0% <ø> (ø)	⬆️
TezosKit/Conseil/GetOriginatedContractsRPC.swift	0% <0%> (ø)
TezosKit/Conseil/ConseilClient.swift	12.65% <0%> (-0.5%)	⬇️
Extensions/PromiseKit/ConseilClient+Promises.swift	0% <0%> (ø)	⬆️
TezosKit/Conseil/Transaction.swift	100% <0%> (ø)	⬆️

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