badges, PyYAML + pre-testing fixes

**`.gitignore`**: .tox dir will be the basis for Python virtualenv dirs for testing

**`.travis.yml`**: added libyaml OS library packages

**`README.md`**:
 - dynamic PyPI badge (no assembly req)
 - gemnasium dependency hooks (change branch to master on gemnasium if it doesn't work - it also might need one commit to become active)

**`development.txt`**:  specific versions for testing

**`requirements.txt`**: added PyYAML - should probably also use specific MAJOR.MINOR versions (>=) like
setup.py / [semver](http://semver.org/)