use accurate version comparison
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
upgrade to rspec 3.x

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

Resolves:

    go: missing Mercurial command. See http://golang.org/s/gogetcmd
    package code.google.com/p/goauth2/oauth: exec: "hg": executable file not found in $PATH
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