{
    "name": "snowdog/theme-blank-sass",
    "description": "SASS based version of Magento 2 Blank theme",
    "version": "0.5.2",
    "license": "MIT",
    "type": "magento2-theme",
    "require": {
      "php": "~5.5.0|~5.6.0|~7.0.0",
      "magento/framework": "100.0.*"
    },
    "autoload": {
        "files": [
            "registration.php"
        ]
    }
}

{
    "name": "snowdog/theme-blank-sass",
    "description": "SASS based version of Magento 2 Blank theme",
    "version": "0.5.2",
    "license": "MIT",
    "type": "magento2-theme",
    "require": {
      "php": "~5.5.0|~5.6.0|~7.0.0",
      "magento/framework": "^100.0.0"
    },
    "autoload": {
        "files": [
            "registration.php"
        ]
    }
}

Make Package installable in 2.1
Make Package installable in 2.1

Magento 2.1 requires magento-framework 100.1.0-rc1 which is not covered by 100.0.*
The ^ version constraint is designe for semantic versioning and should be used here I think. This will allow any subversion of the 100 Major Version