doc: Documents the begin/end arguments to ipfs.files.cat and friends

Author: achingbrain

SPEC/FILES.md

@@ -159,9 +159,9 @@ pull(
 
 ##### `Go` **WIP**
 
-##### `JavaScript` - ipfs.files.cat(ipfsPath, [callback])
+##### `JavaScript` - ipfs.files.cat(ipfsPath, [options], [callback])
 
-ipfsPath can be of type:
+`ipfsPath` can be of type:
 
 - [`cid`][cid] of type:
   - a [CID](https://github.com/ipfs/js-cid) instance
@@ -172,6 +172,10 @@ ipfsPath can be of type:
   - '/ipfs/QmXEmhrMpbVvTh61FNAxP9nU7ygVtyvZA8HZDUaqQCAb66/a.txt'
   - 'QmXEmhrMpbVvTh61FNAxP9nU7ygVtyvZA8HZDUaqQCAb66/a.txt'
 
+`options` is an optional object that may contain the following keys:
+  - `offset` is an optional byte offset to start the stream at
+  - `count` is an optional number of bytes to read from the stream
+
 `callback` must follow `function (err, file) {}` signature, where `err` is an error if the operation was not successful and `file` is a [Buffer][b]
 
 If no `callback` is passed, a promise is returned.
@@ -196,9 +200,9 @@ A great source of [examples][] can be found in the tests for this API.
 
 ##### `Go` **WIP**
 
-##### `JavaScript` - ipfs.files.catReadableStream(ipfsPath) -> [Readable Stream][rs]
+##### `JavaScript` - ipfs.files.catReadableStream(ipfsPath, [options]) -> [Readable Stream][rs]
 
-ipfsPath can be of type:
+`ipfsPath` can be of type:
 
 - [`cid`][cid] of type:
   - a [CID](https://github.com/ipfs/js-cid) instance
@@ -209,6 +213,10 @@ ipfsPath can be of type:
   - '/ipfs/QmXEmhrMpbVvTh61FNAxP9nU7ygVtyvZA8HZDUaqQCAb66/a.txt'
   - 'QmXEmhrMpbVvTh61FNAxP9nU7ygVtyvZA8HZDUaqQCAb66/a.txt'
 
+`options` is an optional object that may contain the following keys:
+  - `offset` is an optional byte offset to start the stream at
+  - `count` is an optional number of bytes to read from the stream
+
 Returns a [Readable Stream][rs] with the contents of the file.
 
 
@@ -225,9 +233,9 @@ A great source of [examples][] can be found in the tests for this API.
 
 ##### `Go` **WIP**
 
-##### `JavaScript` - ipfs.files.catPullStream(ipfsPath) -> [Pull Stream][rs]
+##### `JavaScript` - ipfs.files.catPullStream(ipfsPath, [options]) -> [Pull Stream][rs]
 
-ipfsPath can be of type:
+`ipfsPath` can be of type:
 
 - [`cid`][cid] of type:
   - [Buffer][b], the raw Buffer of the cid
@@ -237,6 +245,10 @@ ipfsPath can be of type:
   - '/ipfs/QmXEmhrMpbVvTh61FNAxP9nU7ygVtyvZA8HZDUaqQCAb66/a.txt'
   - 'QmXEmhrMpbVvTh61FNAxP9nU7ygVtyvZA8HZDUaqQCAb66/a.txt'
 
+`options` is an optional object that may contain the following keys:
+  - `offset` is an optional byte offset to start the stream at
+  - `count` is an optional number of bytes to read from the stream
+
 Returns a [Pull Stream][ps] with the contents of the file.
 
 ```JavaScript