Remove PHP 5.4 features.

Remove shorthand array syntax
Remove callable typehint
Boo.
Merge pull request #35 from chadicus/master

Remove PHP 5.4 array syntax. Boo.
Add documentation for the Filterer behavior.

This defines the specification that the filterer is given and hopefully
makes it a bit easier to understand, although that's a tough task ;)
Merge pull request #37 from nubs/master

Add documentation for the Filterer behavior.
Add email filter

For some cases it is good enough to just call `filter_var` in the filter spec like this:

```php
$filters = ['email' => [['filter_var', FILTER_VALIDATE_EMAIL]];
```

However `filter_var` will return `false` on failure which means you must do a follow up call to either check for the false value or add a `string` filter after the `filter_var` call like this:

```php
$filters = ['email' => [['filter_var', FILTER_VALIDATE_EMAIL], ['string']];
```

This will result in an error messages saying `false` is not a string. which is not a very descriptive error for an invalid email.
Merge pull request #38 from chadicus/email

Add email filter
Update to phpunit 4.
Enable strict phpunit tests.
Use PHPUnit as a library rather than via CLI.

This makes things less fragile.  See dominionenterprises/util-php#32 for
more details.
Merge pull request #39 from nubs/phpunit-as-a-library

Access PHPUnit as a library for gathering report
Remove clover.xml from gitignore.
Use the full path for code coverage.
Use phpcs as a library.
Use shields.io flat svg badges.
Remove --dev from composer install.

--dev is the default.
Merge pull request #40 from nubs/master

Update build scripts to use phpcs as a library.
Create a docker/fig based build.
Merge pull request #41 from nubs/master

Create a docker/fig based build.