Updated Changelog (markdown)

Changelog.md

@@ -4,13 +4,19 @@ This change log tracks the releases on our [pilot server](https://recodex.mff.cu
 
 | Date | [web-app](https://github.com/ReCodEx/web-app/releases) | [api](https://github.com/ReCodEx/api/releases) | [worker](https://github.com/ReCodEx/worker/releases) | [broker](https://github.com/ReCodEx/broker/releases) | [fileserver](https://github.com/ReCodEx/fileserver/releases) | [monitor](https://github.com/ReCodEx/monitor/releases) |
 | --- |:---:|:---:|:---:|:---:|:---:|:---:|
+| 1.5.2018      |  v1.8.1  |  v1.8.3  |  v1.4.1  |  v1.2.1  |  v1.2.1  |  v1.0.0  |
 | 29.4.2018     |  v1.8.0  |  v1.8.2  |  v1.4.1  |  v1.2.1  |  v1.2.1  |  v1.0.0  |
 | 20.4.2018     |  v1.7.2  |  v1.8.1  |  v1.4.0  |  v1.2.1  |  v1.2.1  |  v1.0.0  |
 | 17.4.2018     |  v1.7.2  |  v1.8.0  |  v1.4.0  |  v1.2.1  |  v1.2.1  |  v1.0.0  |
-| 14.4.2018     |  v1.7.1  |  v1.8.0  |  v1.4.0  |  v1.2.0  |  v1.2.1  |  v1.0.0  |
 
 Older versions are at the bottom of this page.
 
+### 1.5.2018
+
+* Button for downloading best solutions in a ZIP archive added to Group Detail page.
+* Fixing multiple bugs.
+* Improving appearance and user experience.
+
 ## 29.4.2018
 
 * Introducing data-only exercises (the user submits only data which are validated by custom judge).
@@ -119,6 +125,7 @@ Older versions are at the bottom of this page.
 
 | Date | [web-app](https://github.com/ReCodEx/web-app/releases) | [api](https://github.com/ReCodEx/api/releases) | [worker](https://github.com/ReCodEx/worker/releases) | [broker](https://github.com/ReCodEx/broker/releases) | [fileserver](https://github.com/ReCodEx/fileserver/releases) | [monitor](https://github.com/ReCodEx/monitor/releases) |
 | --- |:---:|:---:|:---:|:---:|:---:|:---:|
+| 14.4.2018     |  v1.7.1  |  v1.8.0  |  v1.4.0  |  v1.2.0  |  v1.2.1  |  v1.0.0  |
 | 28.3.2018     |  v1.7.0  |  v1.7.0  |  v1.3.0  |  v1.2.0  |  v1.2.1  |  v1.0.0  |
 | 4.3.2018      |  v1.6.2  |  v1.6.2  |  v1.3.0  |  v1.2.0  |  v1.2.1  |  v1.0.0  |
 | 26.2.2018     |  v1.6.1  |  v1.6.1  |  v1.3.0  |  v1.2.0  |  v1.2.1  |  v1.0.0  |