Release 0.4.0 of Pravega Samples

Some highlights of this release:

- created sql sample application to demonstrate the use of Pravega Table API
- added samples to demonstrate the use of StreamCuts API with Flink
- added sample application to demonstrate terasort on Pravega using connectors

This release includes the following list of commits (6f4edb0..v0.3.2):

commit 6f4edb0f4ef7c1f77736ee8096d8a035b648aad6
Author: Raśl Gracia <raulgraciatinedo@gmail.com>
Date:   Fri Feb 8 19:43:54 2019 +0100

    [Issue-168]: Update artifact versions to 0.4.0 and related fixes (#173)
    
    * Updated Pravega, Flink and Hadoop connector version to 0.4.0
    * Updated samples version to 0.4.0
    * Fixed minor issues from Hadoop samples
    
    Signed-off-by: Raśl Gracia <raul.gracia@emc.com>

commit 9deadbca2f6cb94617cf50f90c745954a9a3361b
Author: Vijay Srinivasaraghavan <vijikarthi@yahoo.com>
Date:   Wed Jan 23 08:46:26 2019 -0800

    [Issue-159] Create SQL sample for Flink Connector (#166)
    
    * Creates sample application to demonstrate the use of Flink connector Table API/SQL
    
    Signed-off-by: Vijay Srinivasaraghavan <vijayaraghavan.srinivasaraghavan@emc.com>

commit df6f453fbea086d4efd96ebd3e822d751c46d341
Author: Kevin Han <kevin.han1@emc.com>
Date:   Mon Jan 14 09:51:48 2019 -0800

    [issue-162] improve the performance of Pravega based Terasort sample code (#164)
    
    * Made segments of stream configurable as the
    existing 3 segments are too limited for large
    scale performance test;
    
    * Changes back to the approach using multiple
    streams with fixed(1) segment for terasort output
    
    
    Signed-off-by: kevinhan88 <kevinhan88@gmail.com>

commit 50353f7f2a08e0328ada35a93a0b845fe77a7f84
Author: Raśl Gracia <raulgraciatinedo@gmail.com>
Date:   Fri Nov 9 21:16:58 2018 +0100

    Issue 160: Use new StreamCuts API call to get the end of a Stream slice (#161)
    
    Use new StreamCuts API call in Flink StreamCuts sample to get the end of a stream slice.
    
    Signed-off-by: Raśl Gracia <raul.gracia@emc.com>

commit deeb683981c57f1f4f4af4c3535cb40a2bf4f535
Author: Hongyu Han <kevinhan88@gmail.com>
Date:   Wed Oct 17 09:56:39 2018 -0700

    [issue-150] Add Hadoop TeraSort support using Pravega Streams (#152)
    
    Sample code to run Terasort using Pravega streams.
    
    Signed-off-by: kevinhan88 <kevinhan88@gmail.com>

commit 634bf5c0601c298fa99b9c762686f53bcce5246d
Author: Vijay Srinivasaraghavan <vijikarthi@yahoo.com>
Date:   Thu Sep 13 10:57:18 2018 -0700

    [issue-148] Update Flink version to 1.6.0 (#149)
    
    * [issue-148] Update Flink version to 1.6.0
      * Updated flink connector version that was built for Flink 1.6.0
    
    Signed-off-by: Vijay Srinivasaraghavan <vijayaraghavan.srinivasaraghavan@emc.com>

commit 8ae4ec4eba7771fee77225d09721f2286afb9810
Author: Raśl Gracia <raulgraciatinedo@gmail.com>
Date:   Wed Sep 12 20:13:04 2018 +0200

    Issue 91: Flink StreamCuts Sample (#147)
    
    This application demonstrates how to use Pravega StreamCuts in a Flink application.

commit 0678e9f1a2d059d4ca6de18a692a49b575b089d8
Author: yangb8 <bo.yang@emc.com>
Date:   Thu Aug 16 03:36:13 2018 -0400

    Sample code of using streamcut with Hadoop connector (#138)
    
    * Extended wordcount sample to use StreamCuts with Hadoop connector.
    
    Signed-off-by: Bo Yang <b.yang@emc.com>

commit 9e5ade8856595be3416ef130837b0303d8f7e5a3
Author: Raśl Gracia <raulgraciatinedo@gmail.com>
Date:   Thu Aug 2 21:56:16 2018 +0200

    Issue 145: Fixed samplesVersion in develop branch. (#146)
    
    Signed-off-by: Raśl Gracia <raul.gracia@emc.com>

commit b9f4fda1a1d30ac79e6e3b4f4ee3d22b3535d48a
Author: Raśl Gracia <raulgraciatinedo@gmail.com>
Date:   Fri Jul 20 16:59:03 2018 +0200

    Issue 135: Avoid accessing checkpoint positions to get stream cuts. (#136)
    
    Signed-off-by: Raśl Gracia <raul.gracia@emc.com>

commit 7539cbf5d9c10f2e2865079f4de15bcef7170afa
Author: Raśl Gracia <raulgraciatinedo@gmail.com>
Date:   Mon Jul 2 08:36:38 2018 +0200

    Issue 130: Updated artifacts version to 0.4.0. (#134)
    
    Pravega dependency artifacts have been updated to version 0.4.0.
    
    Signed-off-by: Raśl Gracia <raul.gracia@emc.com>

commit 725834537969294f4d5b91f4e6eaedf99126d35e
Author: Vijay Srinivasaraghavan <vijikarthi@yahoo.com>
Date:   Fri Jun 22 18:27:00 2018 -0700

    [issue-125] Update develop branch to r0.3 (#129)
    
    * updated pravega, flink and hadoop connector version to 0.3.0
    * update samples version to 0.3.0
    
    Signed-off-by: Vijay Srinivasaraghavan <vijayaraghavan.srinivasaraghavan@emc.com>