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

Author: achingbrain

SPEC/FILES.md

@@ -161,9 +161,9 @@ pull(
 
 ##### `Go` **WIP**
 
-##### `JavaScript` - ipfs.files.cat(ipfsPath, [callback])
+##### `JavaScript` - ipfs.files.cat(ipfsPath, [begin], [end], [callback])
 
-ipfsPath can be of type:
+`ipfsPath` can be of type:
 
 - [`cid`][cid] of type:
   - [Buffer][b], the raw Buffer of the cid
@@ -173,6 +173,8 @@ ipfsPath can be of type:
   - '/ipfs/QmXEmhrMpbVvTh61FNAxP9nU7ygVtyvZA8HZDUaqQCAb66/a.txt'
   - 'QmXEmhrMpbVvTh61FNAxP9nU7ygVtyvZA8HZDUaqQCAb66/a.txt'
 
+`begin` is an optional byte offset to start the stream at
+`end` is an optional byte offset to stop the stream before
 `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.
@@ -197,9 +199,9 @@ 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, [begin], [end]) -> [Readable Stream][rs]
 
-ipfsPath can be of type:
+`ipfsPath` can be of type:
 
 - [`cid`][cid] of type:
   - [Buffer][b], the raw Buffer of the cid
@@ -209,6 +211,9 @@ ipfsPath can be of type:
   - '/ipfs/QmXEmhrMpbVvTh61FNAxP9nU7ygVtyvZA8HZDUaqQCAb66/a.txt'
   - 'QmXEmhrMpbVvTh61FNAxP9nU7ygVtyvZA8HZDUaqQCAb66/a.txt'
 
+`begin` is an optional byte offset to start the stream at
+`end` is an optional byte offset to stop the stream before
+
 Returns a [Readable Stream][rs] with the contents of the file.
 
 
@@ -225,9 +230,9 @@ 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, [begin], [end]) -> [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 +242,9 @@ ipfsPath can be of type:
   - '/ipfs/QmXEmhrMpbVvTh61FNAxP9nU7ygVtyvZA8HZDUaqQCAb66/a.txt'
   - 'QmXEmhrMpbVvTh61FNAxP9nU7ygVtyvZA8HZDUaqQCAb66/a.txt'
 
+`begin` is an optional byte offset to start the stream at
+`end` is an optional byte offset to stop the stream before
+
 Returns a [Pull Stream][ps] with the contents of the file.
 
 ```JavaScript