Close out various old issues, add CoinJoin support, & update deps

[coolaj86]

Summary:

• Refactor private key handling by removing convenience methods and dependency injection as to be more clear and less error-prone
• Fix longstanding hidden bug in pubKeyHash script construction
• Add many tests
• Add Transaction Parser, and many complementary tests
• Various documentation typo fixes, dev dependency updates, and test updates

PRs:

• doc+fix sign() args, txId, sigBuf #44
• feat: private export of internal utils and constants for monkey-patching #45
• fix: scope keyUtils to hashAndSignAll lifecycle #46
• ref: ditch confusing dependency injection #47
• chore: minor cleanup and doc typos #48
• chore: minor cleanup and doc typos (corrected) #49
• ref: ditch confusing dependency injection (corrected) #50
• fix: accept txid (canonical) or txId (deprecated, from insight) #52
• add parser for various transaction types #53
• fix: pkh script #55
• fix: allow 0-length memos (to burn dust) #56
• ref! only support getPrivateKey(), drop keys array #57
• doc: fix privKeyBytes typos #58
• fix doc and access order of txid #59
• ref+feat: separate to hash each input individually (for CoinJoin) #60
• feat: add option to create the sighash tx with the trailing sighash byte #61
• chore: update dev dep dashkeys for testnet fixes #62
• chore: update dev dep dashkeys for testnet fixes #63
• workaround: don't require priv keys to match for now #64