Progress callback fix and code refactoring

Fix a problem with the progress where at the end of the compress or extract it never shows 100.
Refactor the code of the library to be more readable.

Progress callback fix

Fix incorrect data reporting for the progress callback.

Remove native dependency

Remove the native dependency on Windows and use 7za through 7zip-bin to correct problem #1.

Scope name and general fix

This version brings a general fix to the project:

• Add .gitignore
• Remove node-pre-gyp since @mapbox/node-pre-gyp is installed
• Upgrade package version

Also, the package now use a scope name: @steezcram/sevenzip available here. The non-scope version is now deprecated.

API stability

Increase API stability:

• better check for the parameters
• the progressCallback is now not a mandatory parameter

The package now installs the new version of node-pre-gyp when you install the package through the npm install / yarn add command.

Fixes

Fix the problem when installing the module and typos correction in the documentation.

Cross-platform support

Adding cross-platform support through 7zz for macOS et Linux.

All the commands are supported as well as all the common parameters.