Git doesn't ignore .idea and composer.phar

Developer-specific files like `.idea` can be ignored globally:

```
[core]
excludesFile = ~/.gitignore
```

composer.phar shouldn't be hanging around in this directory.
Git ignores composer.lock; this is a lib, not an app.
PHPUnit via composer require-dev.
PSR-1 and PSR-2 fixes via http://cs.sensiolabs.org/
Overhaul: PHP namespaces and PSR-4 layout.
README updated for Pheanstalk v3.0.
build_phar.php updated for PSR-4 etc.
composer.json alias dev-master to 3.x-dev, was 2.x-dev.
composer.json more permissive for PHPUnit version.
PHP 5.6 added to Travis build.
Accumulate read data in string instead of array.

The array version uses a lot of memory.