Make Golint happy in the blocks submodule.

This has required changing the order of some parameters and
adding HashOnRead to the Blockstore interface (which I have in turn
added to all the wrapper implementations).

License: MIT
Signed-off-by: Hector Sanjuan <hector@protocol.ai>

blocks.go

-// package blocks contains the lowest level of IPFS data structures,
-// the raw block with a checksum.
+// Package blocks contains the lowest level of IPFS data structures.
+// A block is raw data accompanied by a CID. The CID contains the multihash
+// corresponding to the block.
 package blocks
 
 import (
@@ -11,8 +12,11 @@ import (
 	mh "gx/ipfs/QmbZ6Cee2uHjG7hf19qLHppgKDRtaG4CVtMzdmK9VCVqLu/go-multihash"
 )
 
-var ErrWrongHash = errors.New("data did not match given hash!")
+// ErrWrongHash is returned when the Cid of a block is not the expected
+// according to the contents. It is currently used only when debugging.
+var ErrWrongHash = errors.New("data did not match given hash")
 
+// Block provides abstraction for blocks implementations.
 type Block interface {
 	RawData() []byte
 	Cid() *cid.Cid
@@ -20,7 +24,8 @@ type Block interface {
 	Loggable() map[string]interface{}
 }
 
-// Block is a singular block of data in ipfs
+// A BasicBlock is a singular block of data in ipfs. It implements the Block
+// interface.
 type BasicBlock struct {
 	cid  *cid.Cid
 	data []byte
@@ -32,9 +37,9 @@ func NewBlock(data []byte) *BasicBlock {
 	return &BasicBlock{data: data, cid: cid.NewCidV0(u.Hash(data))}
 }
 
-// NewBlockWithHash creates a new block when the hash of the data
+// NewBlockWithCid creates a new block when the hash of the data
 // is already known, this is used to save time in situations where
-// we are able to be confident that the data is correct
+// we are able to be confident that the data is correct.
 func NewBlockWithCid(data []byte, c *cid.Cid) (*BasicBlock, error) {
 	if u.Debug {
 		chkc, err := c.Prefix().Sum(data)
@@ -49,22 +54,27 @@ func NewBlockWithCid(data []byte, c *cid.Cid) (*BasicBlock, error) {
 	return &BasicBlock{data: data, cid: c}, nil
 }
 
+// Multihash returns the hash contained in the block CID.
 func (b *BasicBlock) Multihash() mh.Multihash {
 	return b.cid.Hash()
 }
 
+// RawData returns the block raw contents as a byte slice.
 func (b *BasicBlock) RawData() []byte {
 	return b.data
 }
 
+// Cid returns the content identifier of the block.
 func (b *BasicBlock) Cid() *cid.Cid {
 	return b.cid
 }
 
+// String provides a human-readable representation of the block CID.
 func (b *BasicBlock) String() string {
 	return fmt.Sprintf("[Block %s]", b.Cid())
 }
 
+// Loggable returns a go-log loggable item.
 func (b *BasicBlock) Loggable() map[string]interface{} {
 	return map[string]interface{}{
 		"block": b.Cid().String(),