Update the descriptions for the packages: elasticdl_client and elasticdl_preprocessing (#2127)

* Add the description for the elasticdl_client package.

* Update the description for elasticdl_preprocessing and elasticdl_client.

Author: brightcoder01

setup_client.py

@@ -19,7 +19,12 @@
 setup(
     name="elasticdl_client",
     version="develop",
-    description="The client tool for ElasticDL.",
+    description="The client command line tool for ElasticDL.",
+    long_description="ElasticDL Client is the client command line tool for"
+    "ElasticDL. It's convenient with it to build and push Docker images for"
+    "a distributed ElasticDL job. And then we can use it to submit a train, "
+    "evaluate or predict job to a Kubernetes cluster.",
+    long_description_content_type="text/markdown",
     author="Ant Financial",
     url="https://elasticdl.org",
     install_requires=required_deps,

setup_preprocessing.py

@@ -23,7 +23,7 @@
 setup(
     name="elasticdl_preprocessing",
     version="develop",
-    description="A Kubernetes-native Deep Learning Framework",
+    description="A feature preprocessing library.",
     long_description="This is an extension of the native Keras Preprocessing"
     " Layers and Feature Column API from TensorFlow. We can develop our model"
     " using the native high-level API from TensorFlow and our library."