Renames property `repoType` to `repoName`

Renames property `repoType` to `repoName`

Fixes #17

Since we're in a really early stage, I don't think we need to keep the old name and deprecate
this was using the wrong term before. We thought this property defined the type of repo you wanted to upload to (in bintray), but this is actually the name of the repo you want to upload to.

i.e. you can have multiple maven repos in your bintray account (android-libs, java-libs, gradle-plugins, etc.), this property allows you to chose which repo you want to upload to.

The bintray plugin uses `repo`, but I think `repoName` makes it more explicit (https://github.com/bintray/gradle-bintray-plugin/blob/master/src/main/groovy/com/jfrog/bintray/gradle/BintrayExtension.groovy#L43)