fix(core/components/dag): make options in put API optional

The [dag.put](https://github.com/ipfs/interface-ipfs-core/blob/master/SPEC/DAG.md#dagput) interface
takes an options object which is required, but should be optional with
decent defaults.

See dedicated test here: ipfs-inactive/interface-js-ipfs-core#316

This commit implements this behaviour.

**Before**:

```js
ipfs.dag.put(obj, options, (err, cid) => {...});
```

^ Prior to this commit, without passing `options`, this call resulted in an error.

**After**:

```js
ipfs.dag.put(obj, (err, cid) => {...});
```

^ This is now perfectly fine.

Fixes ipfs#1395

License: MIT
Signed-off-by: Pascal Precht <pascal.precht@gmail.com>

src/core/components/dag.js

@@ -9,6 +9,17 @@ const flattenDeep = require('lodash.flattendeep')
 module.exports = function dag (self) {
   return {
     put: promisify((dagNode, options, callback) => {
+      if (typeof options === 'function') {
+        callback = options
+      }
+
+      const optionDefaults = {
+        format: 'dag-pb',
+        hashAlg: 'sha2-256'
+      }
+
+      options = options.cid ? options : Object.assign({}, optionDefaults, options)
+
       self._ipld.put(dagNode, options, callback)
     }),