Remove log4j usage

[machielg]

In com.tngtech.jgiven.impl.util.ReflectionUtil there is a reference to log4j. This seems to be inconsistent with the usage of slf4j in the rest of the project. This means I can't use JGiven in a project that uses a different slf4j back-end.

Switching to the slf4j Logger seems to be trivial.

[aaschmid]

I have moved "slf4j-log4j12" to "test" scope which causes

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.

while executing tests. @janschaefer do you have any clue why as it there should be an implementation on classpath while executing tests, isn' it?

[aaschmid]

Analysing this "problem" further, it seems that just the "slf4-jog4j12" test dependency is not handled transitive in the other subprojects, even if "jgiven-core/test-jar" is required as dependency ... this is because Maven is not designated for that, see https://jira.codehaus.org/browse/MNG-1378 :-(

[janschaefer]

@aaschmid thanks for looking into that!

[janschaefer]

If I see it correctly, the Maven defect is already 9 years old and not fixed yet! I will have a look whether we can get rid of the test-jar dependency altogether.

[janschaefer]

This also finally convinced me that we should actually switch to Gradle #39

[janschaefer]

I have merged the branch into master and deleted it.