Full support of periods in property name and property path

[A-312]

fix: #250, fix: #271, fix: #315

This PR adds the full support of periods in property name and property path.

config.get('db.host');
// or
config.get('db').host;
// also
config.get('db[0]');
// with dot:
config.get('db["www.airbus.com"]'); { 'db': { 'www.airbus.com': 'air company'} }
// in the first level
config.get("['foo.bar']"); // { 'foo.bar': 'baz' }

[coveralls]

Coverage remained the same at 100.0% when pulling 8cadd2a on A-312:dot-support into 30bcc2e on mozilla:feat-multi-packages-split.

[A-312]

I got issue with backslash and path, I will make a fix : https://github.com/mike-marcacci/objectpath/issues