Use git -C for setting working dir

It is way better to tell git which dir to use instead of actually changing the current directory.
Use git clone --local instead of -l

Short command line options are meant to be typed.
Only long ones should be used in code to be easily understood.
Use composer --working-dir

Similar to git -C it better to tell Composer which working directory to use
instead of actually changing the working directory.

Another small nit is that the `--dev` option is now the default.
It may be removed in the future.
Use `--no-dev` if you want only the `require` section to be used.
Move source file one dir up using PSR-4

Nesting source files into a directory with the same name
as the top namespace is a limitation of PSR-0.

Now when Composer supports PSR-4 why not take an advantage?
Merge pull request #7 from lox/working-dir

Set working dir instead of changing it
Merge pull request #8 from lox/psr-4

Move source file one dir up using PSR-4
Require symfony/console
Organize benchmarking in its own classes

New classes:
- Regreph\Bench\Bench - given an array of test cases it runs the tests and gives the bench results
- Regreph\Bench\BenchFile - give it a file and it will extract the tests and load them into a Bench instance
- Regreph\Bench\BenchResults - holds the bench results in an array of TestResult instances and more

Moved classes:
- Regreph\TestCase is now Regreph\TestCase\TestCase
- Regreph\TestCaseFinder is now Regreph\TestCase\TestCaseFinder
- Regreph\TestResult is now Regreph\Bench\TestResult
Make regreph a console app with two commands

`bin/regreph` is now a `symfony/console` application with two commands:
 - bench - bench a library based on a test file
 - regreph - bench the working dir and a past refspec of a library and compare the results

The regreph command is no longer using the bench command through the shell.
Instead it is using the common Regreph\Bench classes to perform the benchmarking.

---

WORK IN PROGRESS
================

The `regreph` command is still work in progress

One of thie things not working right now is the benchmarking of the refspec.
It does not find the tests.
Make Bench classes immutable

Bench and BenchFile are now immutable.
You cannot change their results/file after they've been constructed.

You can no longer set the whole results array on a BenchResults instance.
You could just add test results to the instance.

The setters were not really needed and this ensures the results stay
the same.