Feat/module docs #83 (#267)

Add READMEs to all modules
Co-authored-by: Ingar Shu <ingar@users.noreply.github.com>

Author: shannonwells

pieceio/README.md

@@ -0,0 +1,54 @@
+# pieceio
+
+The pieceio module is a collection of structs for generating piece commitments (a.k.a. CommP) and 
+storing pieces for storage market deals. It is used by the 
+[`storagemarket`](../storagemarket) module.
+
+## Installation
+```bash
+go get github.com/filecoin-project/go-fil-markets/pieceio
+```
+
+## PieceIO
+`PieceIO` is used by [`storagemarket`](../storagemarket) client for proposing deals. 
+
+**To initialize a PieceIO:**
+```go
+package pieceio
+
+func NewPieceIO(carIO CarIO, bs blockstore.Blockstore) PieceIO
+```
+**Parameters**
+* `carIO` is a [CarIO](#CarIO) from this module
+* `bs` is an IPFS blockstore for storing and retrieving data for deals. See
+ [github.com/ipfs/go-ipfs-blockstore](github.com/ipfs/go-ipfs-blockstore).
+
+## PieceIOWithStore
+`PieceIOWithStore` is `PieceIO` with a [`filestore`](../filestore). It is used by 
+[`storagemarket`](../storagemarket) provider to store pieces, and to generate and store piece commitments
+ and piece metadata for deals. 
+ 
+**To initialize a PieceIOWithStore:**
+
+```go
+package pieceio
+
+func NewPieceIOWithStore(carIO CarIO, store filestore.FileStore, bs blockstore.Blockstore) PieceIOWithStore
+```
+**Parameters**
+* `carIO` is a [CarIO](#CarIO) from this module
+* `store` is a [FileStore](../filestore) from this go-fil-markets repo.
+* `bs` is an IPFS blockstore for storing and retrieving data for deals. See
+ [github.com/ipfs/go-ipfs-blockstore](github.com/ipfs/go-ipfs-blockstore).
+
+## CarIO
+CarIO is a utility module that wraps [github.com/ipld/go-car](https://github.com/ipld/go-car) for use by storagemarket.
+
+**To initialize a CarIO:**
+```go
+package cario
+
+func NewCarIO() pieceio.CarIO
+```
+
+Please the [tests](pieceio_test.go) for more information about expected behavior.