Resolves issue #4 (API for measurements)

There's an assumption in the serializer for measurements that
observations are nested dictionaries, with values as escaped string
representations of JSON objects.
Formatting fix
Stupid markdown not linkifying localhost.
Add nice geo-serialization

Introduces a new requirement, but gives us location serializations like:

    "location": {
        "type": "Point",
        "coordinates": [
            -3.55378735554,
            52.4424721842
        ]
    }

instead of:

    "location": "POINT (-3.5537873555399999 52.4424721841999997)",

Nice.
Merge branch 'api' of github.com:jimr/openwater into api
Merge pull request #8 from jimr/api

Resolves issue #4 (API for measurements)