Even faster shortening and expanding via direct GMP usage

All credits for performence improvements goes to marvelous @Ocramius.
Now, 100x faster than before!

Much faster shortening and expanding via direct GMP usage

• Added GMP based strategy for faster UUID shortening
• New (prefered) static constructor for Shortener which makes it much easier for instantiate

Replacing abandoned moontoast/math with brick/math

Merge pull request #8 from marmichalski/brick

Replace abandoned moontoast/math with brick/math

Fix for PHP 7.2 and 7.3 builds in Travis CI

Merge pull request #7 from mgrajcarek/fix/composer-lock-72

Fix for travis build on PHP 7.2 and 7.3

Minimum PHP version bumped to 7.2 and Psalm support

Thank you @Ocramius for contribution!

Fix for str_pad

Fix from @Ocramius for incorrect str_pad usage.

Travis CI expanded to PHP 7.2, 7.3 and 7.4

Merge pull request #3 from open-source-contributions/test_enhancement

Test enhancement

Public API change

Typos fixed by @EvulMastah
Charset changed to CharsSet

Composer meta data update and fixes

Merge pull request #1 from EvulMastah/composer

Update composer package data

Description updates, travis and formatter fix

Travis has been added as a build tool.
README.md updated - now containing example of expanding short UUID to full hexadecimal format.