remove gemfile lock during bootstrap
fix test failure due to upstream rubocop changes

* bbatsov/rubocop@ff167d8f changed Rubocop -> RuboCop
* require min version of rubocop to ensure bundle has the above commit
latest rubocop now prefers backticks over %x

upstream rubocop now recommends to use backticks instead of %x
use rspec-expectations 3.x for test harness

adapt to breaking changes in rspec-expectations 3
https://www.relishapp.com/rspec/rspec-expectations/v/3-0/docs/changelog
rspec/mocha now requires symbol for mock_with

Resolves error:

    Unknown mocking framework: "mocha".
    Pass a module or one of [:rspec, :flexmock, :rr, :mocha, :nothing]
run spec_standalone to support old and current rake tasks

Latest bundle seems to not invoke :spec_standalone from :spec,
so invoke it directly. This ensures the harness runs regardless
of which bundle is installed.
volumesfrom is now in hostconfig, not config
add tools to work with mercurial repositories
update all packages in base image at build-time
add host and dig commands to devenv
add ftp and tftp clients

These are useful for testing other services.
use the "semi-official" fedora 20 base image