Remove unused dep.

packages/xen-api/package.json

@@ -39,7 +39,6 @@
     "lodash.foreach": "^3.0.2",
     "lodash.isarray": "^3.0.2",
     "lodash.isobject": "^3.0.1",
-    "lodash.isstring": "^3.0.1",
     "lodash.map": "^3.1.2",
     "lodash.size": "^3.0.0",
     "lodash.startswith": "^3.0.1",

packages/xen-api/src/index.js

@@ -4,7 +4,6 @@ import createDebug from 'debug'
 import forEach from 'lodash.foreach'
 import isArray from 'lodash.isarray'
 import isObject from 'lodash.isobject'
-import isString from 'lodash.isstring'
 import map from 'lodash.map'
 import startsWith from 'lodash.startswith'
 import {BaseError} from 'make-error'