Takeover dbus maintainership

[rblaze]

I'm current maintainer of dbus package. Last release should have tests and benchmarks running fine, no longer depends on chell packages: https://travis-ci.org/rblaze/haskell-dbus/jobs/323798451

Note: build requires libxml2-dev to be installed (via libxml-sax package).

Checklist:

• Meaningful commit message - please not Update build-constraints.yml

• Some time passed since Hackage upload

• On your own machine, in a new directory, you have succesfully run the following set of commands (replace $package with the name of the package that is submitted, $version is the version of the package you want to get into Stackage):

  stack unpack $package
  cd $package-$version
  stack init --resolver nightly
  stack build --resolver nightly --haddock --test --bench --no-run-benchmarks
  

[mihaimaruseac]

Thanks, all is good with the PR.