Upgrading package to PHP 7

Functions now take advantage of PHP 7 Typehints.
Support for PHP 5 has been dropped.

For more information about dropping version support and version numbers, see http://doctrine-project.org/2017/07/25/php-7.1-requirement-and-composer.html and the info under "Why dropping PHP support in a minor version is not a BC break"

More formatting options

Added formatting for accounting notation. e.g. -1.10 => (1.10)
Added format with sign e.g. 1.10 => +1.10

Added .gitattributes so that install from dist should be smaller.

Added shorthand formatting

Added formatShorthand() method.
Removed support for HHVM.