Add vendor dir (#16) (#4)

* Add vendor dir so builds dont require dep

* Pin specific version go-eth version

vendor/github.com/btcsuite/btcd/blockchain/doc.go

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+// Copyright (c) 2013-2014 The btcsuite developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+/*
+Package blockchain implements bitcoin block handling and chain selection rules.
+
+The bitcoin block handling and chain selection rules are an integral, and quite
+likely the most important, part of bitcoin.  Unfortunately, at the time of
+this writing, these rules are also largely undocumented and had to be
+ascertained from the bitcoind source code.  At its core, bitcoin is a
+distributed consensus of which blocks are valid and which ones will comprise the
+main block chain (public ledger) that ultimately determines accepted
+transactions, so it is extremely important that fully validating nodes agree on
+all rules.
+
+At a high level, this package provides support for inserting new blocks into
+the block chain according to the aforementioned rules.  It includes
+functionality such as rejecting duplicate blocks, ensuring blocks and
+transactions follow all rules, orphan handling, and best chain selection along
+with reorganization.
+
+Since this package does not deal with other bitcoin specifics such as network
+communication or wallets, it provides a notification system which gives the
+caller a high level of flexibility in how they want to react to certain events
+such as orphan blocks which need their parents requested and newly connected
+main chain blocks which might result in wallet updates.
+
+Bitcoin Chain Processing Overview
+
+Before a block is allowed into the block chain, it must go through an intensive
+series of validation rules.  The following list serves as a general outline of
+those rules to provide some intuition into what is going on under the hood, but
+is by no means exhaustive:
+
+ - Reject duplicate blocks
+ - Perform a series of sanity checks on the block and its transactions such as
+   verifying proof of work, timestamps, number and character of transactions,
+   transaction amounts, script complexity, and merkle root calculations
+ - Compare the block against predetermined checkpoints for expected timestamps
+   and difficulty based on elapsed time since the checkpoint
+ - Save the most recent orphan blocks for a limited time in case their parent
+   blocks become available
+ - Stop processing if the block is an orphan as the rest of the processing
+   depends on the block's position within the block chain
+ - Perform a series of more thorough checks that depend on the block's position
+   within the block chain such as verifying block difficulties adhere to
+   difficulty retarget rules, timestamps are after the median of the last
+   several blocks, all transactions are finalized, checkpoint blocks match, and
+   block versions are in line with the previous blocks
+ - Determine how the block fits into the chain and perform different actions
+   accordingly in order to ensure any side chains which have higher difficulty
+   than the main chain become the new main chain
+ - When a block is being connected to the main chain (either through
+   reorganization of a side chain to the main chain or just extending the
+   main chain), perform further checks on the block's transactions such as
+   verifying transaction duplicates, script complexity for the combination of
+   connected scripts, coinbase maturity, double spends, and connected
+   transaction values
+ - Run the transaction scripts to verify the spender is allowed to spend the
+   coins
+ - Insert the block into the block database
+
+Errors
+
+Errors returned by this package are either the raw errors provided by underlying
+calls or of type blockchain.RuleError.  This allows the caller to differentiate
+between unexpected errors, such as database errors, versus errors due to rule
+violations through type assertions.  In addition, callers can programmatically
+determine the specific rule violation by examining the ErrorCode field of the
+type asserted blockchain.RuleError.
+
+Bitcoin Improvement Proposals
+
+This package includes spec changes outlined by the following BIPs:
+
+		BIP0016 (https://en.bitcoin.it/wiki/BIP_0016)
+		BIP0030 (https://en.bitcoin.it/wiki/BIP_0030)
+		BIP0034 (https://en.bitcoin.it/wiki/BIP_0034)
+*/
+package blockchain