Remove version from composer.json

[mzeis]

Hi,

composer.json contains a version number:

{
  "name": "cloudplaydev/confluence-php-client",
  "description": "Provides methods for Confluence REST APIs",
  "version": "0.6.0",
  "license": "MIT",`
  /* ... */
}

Composer suggests to remove this field:

composer validate
./composer.json is valid, but with a few warnings
See https://getcomposer.org/doc/04-schema.md for details on the schema
# General warnings
- The version field is present, it is recommended to leave it out if the package is published on Packagist.

Removing it would be helpful, because this way I can test contributions internally beforehand by using my own tags without having to overwrite your composer.json everytime.