Added inverted progressbar movement

[Manawyrm]

This change adds a new configuration option called "invertProgressBar", which can make the remaining time progress bar slide from left to right.

[TimFerrell]

Hi @Manawyrm - this breaks existing tests, and has no tests written for it. If you could resolve those issues, and change the PR to develop then I'd be glad to take a look!

[Manawyrm]

Hello @TimFerrell
thank you for your time, I have now added a test which checks the default state and running direction of the progress bar.

The failing CI tests doesn't really seem to be caused by me:
The error says something about

/home/travis/build/CodeSeven/toastr/node_modules/gulp-task-listing/node_modules/chalk/index.js:2
const escapeStringRegexp = require('escape-string-regexp');
^^^^^
SyntaxError: Use of const in strict mode.

which I imagine is an error in a library that is used.
When running the tests manually, they all go through.