introduced new desc dsl with a block instead of option Hash
Removed unnecessary conditional in `call!`

If `options[:app]` has been set, then it wouldn't get to this code path,
thus rendering the extra check in the call to `builder.run` unnecessary.
This also has the effect of making this code a little easier to read.
Merge pull request #757 from dspaeth-faber/extend_desc_dsl

Proposal: new desc dsl with a block instead of option Hash
Merge pull request #771 from rustygeldmacher/remove_unneeded_conditional

Removed unnecessary conditional in `call!`