should use project not workspace Absolute Path, because some project not under default workspace home dir

[hunthu2000]

when the project source is not under default workspace home dir, junithelper will still create the test class file under workspace home, then user can't see the test file.

replace follow code: String projectRootAbsolutePath = getWorkspaceRootAbsolutePath(getIWorkspaceRoot()) + StringValue.DirectorySeparator.General + projectName + StringValue.DirectorySeparator.General;

with these code: String projectRootAbsolutePath = getIProject(projectName).getLocation() + StringValue.DirectorySeparator.General;

[hunthu2000]

bugfix code commit to: https://github.com/hunthu2000/junithelper