Fix API version comparison for 1.10

v1.10 is current latest: http://docs.docker.io/en/latest/reference/api/docker_remote_api/#v1-10

docker-py fails to compare it due to a float based implementation:

```
>>> from docker import utils
>>> utils.compare_version('1.8', '1.9')
0.09999999999999987
>>> utils.compare_version('1.9', '1.10')
-0.7999999999999998
```

after this change:
```
>>> utils.compare_version('1.8', '1.9')
-1
>>> utils.compare_version('1.9', '1.10')
-1
```