Refactor Ci::Commit and Ci::Build to have all builds for same :sha on single page

This makes Ci::Commit to have only :sha and simplifies routing to have only :sha in path. The :ref and :push_data is now parameter of Ci::Build.

All commit related data (git author, message and .gitlab-ci.yml) is read directly from repository.

All code related for creating builds is moved to CreateBuildsService.

Status deduction is rewritten to make if more efficient and easier to integrate with Commit Status API.

This is partially working, tests are not yet touched.

This slightly changes view of Commit:
![Screen_Shot_2015-10-02_at_15.21.47](https://gitlab.com/gitlab-org/gitlab-ce/uploads/ad3f1ccdcc87659ea437d8db6c5b9f94/Screen_Shot_2015-10-02_at_15.21.47.png)

@dzaporozhets What do you think?


See merge request !1502

This ensures that blocks defines using "benchmark_subject" have access
to methods defined using let/subject & friends.

This class method can be used in "describe" blocks to specify the
subject of a benchmark. This lets you write:

    benchmark_subject { Foo }

instead of:

    benchmark_subject { -> { Foo } }

This benchmark suite uses benchmark-ips
(https://github.com/evanphx/benchmark-ips) behind the scenes. Specs can
be turned into benchmark specs by setting "benchmark" to "true" in the
top-level describe block like so:

    describe SomeClass, benchmark: true do

    end

Writing benchmarks can be done using custom RSpec matchers, for example:

    describe MaruTheCat, benchmark: true do
      describe '#jump_in_box' do
        it 'should run 1000 iterations per second' do
          maru = described_class.new

          expect { maru.jump_in_box }.to iterate_per_second(1000)
        end
      end
    end

By default the "iterate_per_second" expectation requires a standard
deviation under 30% (this is just an arbitrary default for now). You can
change this by chaining "with_maximum_stddev" on the expectation:

    expect { maru.jump_in_box }.to iterate_per_second(1000)
      .with_maximum_stddev(10)

This will change the expectation to require a maximum deviation of 10%.

Alternatively you can use the it block style to write specs:

    describe MaruTheCat, benchmark: true do
      describe '#jump_in_box' do
        subject { -> { described_class.new } }

        it { is_expected.to iterate_per_second(1000) }
      end
    end

Because "iterate_per_second" operates on a block, opposed to a static
value, the "subject" method must return a Proc. This looks a bit goofy
but I have been unable to find a nice way around this.

If this directory were to be empty this would result in warnings being
printed to STDERR, cluttering spec output. Doing this in Ruby fixes this
problem (and also removes the need for shell alltogether).