Kinto2xml

**Bug fix**
- In case there is a diff using xml-verifier, the command now returns an error code (28)

**Internal changes**
- `json2kinto` does not set destination collections as publicly readable (27)

**Breaking changes**
- kinto2xml was renamed amo2kinto (21)
- New JSON Schema file format with a "collection" prefix (22)

**New features**
- Use the schema to validate AMO records in the importer script. (5)
- Warn if the server does not have the schema capability (24)

**Internal changes**
- Document amo2kinto commands: json2kinto, kinto2xml and verifier. (23)

**Initial version**
- Create collection with the definition of the JSON schema.
- Fetch AMO blocklists information from the /blocked/blocklists.json AMO endpoint.
- Handle import configuration on the CLI.
- Bucket / Collection names
- Remote AMO endpoint configuration
- Schema file path configuration
- Schema or not schema
- Verbosity level
- Server selection
- Auth credentials
- Importation type selection
- Support for kinto-signer triggering
- Full SSL support for Python 2.7
- Full Python 2.7 and Python 3.4/3.5 support
- Handle the enabled flag to activate records
- Makefile rule to update the schema definition
- Export kinto blocklists in XML blocklist file version 2
- Export kinto blocklists in XML blocklist file version 3
- XML verifier that create a diff of two XML files