docs(connector): rewrite introduction and form doc structure

docs/source/user_guide/connector/introduction.ipynb

@@ -0,0 +1,80 @@
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+    ".. _`userguide/connector`:\n",
+    "\n",
+    "Connector\n",
+    "=========\n",
+    "\n",
+    "DataPrep.Connector aims to simplify data collection from Web APIs by providing a standard set of operations. \n",
+    "Connector wraps-up complex API calls into a set of easy-to-use Python functions. \n",
+    "By using Connector, you can skip the complex API configuration process and rapidly query different Web APIs in few steps, enabling you to execute the analysis workflow you are familiar with in a direct way."
+   ]
+  },
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+    "Connector offers essential features to facilitate the process of collecting data, for example:\n",
+    "\n",
+    "* Concurrency: Collect data from websites, in parallel, in a fast way!\n",
+    "\n",
+    "* Pagination: Retrieve more rows of a particular query without getting into unnecessary detail about pagination schemes!\n",
+    "\n",
+    "* Authorization: Access more Web APIs quickly! even the ones that implement authorization!\n",
+    "\n",
+    "This section includes a case study for yelp as an example for the process and other sections to explain Connector's functionalities in detail."
+   ]
+  },
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+   },
+   "source": [
+    "## Section Contents\n",
+    "\n",
+    " * [Case study: DBLP API](DBLP.ipynb)\n",
+    " * [Configuration files: usage and composition](config_file.ipynb)\n",
+    " * [connect(): establish the connection and load the configuration files](connect.ipynb)\n",
+    " * [query(): fetch into DataFrames via APIs](query.ipynb)\n",
+    " * [info(): get information of a website](info.ipynb)\n",
+    " * [Authorization schemes supported](authorization.ipynb)\n",
+    " * [Auto-pagination](pagination.ipynb)"
+   ]
+  }
+ ],
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