Integrate Checkstyle into java-reporter-core

[GolubNick]

Add next dependencies:
<plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-checkstyle-plugin</artifactId> <inherited>false</inherited> <version>3.3.0</version> <executions> <execution> <phase>compile</phase> <goals> <goal>check</goal> </goals> </execution> </executions> <configuration> <configLocation>checkstyle.xml</configLocation> <consoleOutput>true</consoleOutput> <failsOnError>true</failsOnError> <linkXRef>false</linkXRef> <sourceDirectories> <sourceDirectory>src/main/java</sourceDirectory> </sourceDirectories> </configuration> </plugin>