fix(package): update cids to version 0.7.0

BREAKING CHANGE: Returned v1 CIDs now default to base32 encoding

Previous versions returned a base58 encoded string when `toString()`/
`toBaseEncodedString()` was called on a CIDv1. It now returns a base32
encoded string.

package.json

@@ -21,7 +21,7 @@
   ],
   "license": "MIT",
   "dependencies": {
-    "cids": "~0.6.0",
+    "cids": "~0.7.0",
     "ethereumjs-account": "^2.0.4",
     "ethereumjs-block": "^2.1.0",
     "ethereumjs-tx": "^1.3.3",