docs: update client-api example

[pinheadmz]

Updates a broken example in /docs brought to my attention by a user on slack:

https://github.com/bcoin-org/bcoin/blob/master/docs/Examples/client-api.js tutorial doesn't work for me. It writes Not enough funds. (available=0.0, required=0.0001078), but in logs I have Balance: { account: 1, tx: 1, coin: 4, unconfirmed: 201840, confirmed: 0 }.

Fixed:

• Funding TX was a coinbase before, but wasn't confirmed so it was blocked by wallet coin selector here: https://github.com/bcoin-org/bcoin/blob/master/lib/primitives/mtx.js#L1789
• getInfo and getblocktemplate should be called from NodeClient not WalletClient
• Specify wallet to retrieve TX details

[codecov-io]

Codecov Report

Merging #667 into master will increase coverage by 0.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #667      +/-   ##
==========================================
+ Coverage    53.2%   53.33%   +0.12%     
==========================================
  Files         104      104              
  Lines       27724    27676      -48     
  Branches     4752     4738      -14     
==========================================
+ Hits        14751    14761      +10     
+ Misses      12973    12915      -58

Impacted Files	Coverage Δ
lib/hd/hd.js	56.14% <0%> (-1.76%)	⬇️
lib/mempool/mempool.js	43.42% <0%> (-1.11%)	⬇️
lib/primitives/keyring.js	69.97% <0%> (-1%)	⬇️
lib/wallet/wallet.js	65.73% <0%> (-0.56%)	⬇️
lib/node/rpc.js	23.38% <0%> (-0.25%)	⬇️
lib/blockchain/chaindb.js	56.78% <0%> (-0.1%)	⬇️
lib/blockchain/chain.js	60.55% <0%> (-0.08%)	⬇️
lib/script/script.js	76.87% <0%> (-0.08%)	⬇️
lib/net/pool.js	15.87% <0%> (-0.05%)	⬇️
lib/wallet/walletdb.js	75.47% <0%> (-0.03%)	⬇️
... and 8 more

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[pinheadmz]

closing this, moving /docs project to #699