Migrate to mavenCentral

[Damien-L]

Since 'jcenter' is deprecated "JCenter Maven repository is no longer receiving updates: newer library versions may be available elsewhere" i think it's a good idea to migrate to mavenCentral.

For those who don't want to use jcenter for their other libraries just add jcenter this way in you build.gradle :

// jcenter will be used only for "com.sergivonavi"
jcenter {
    content {
        includeGroup "com.sergivonavi"
    }
}