Correct some errors in README examples

[henryhallam]

However, it's still not quite right, because I get the following error when trying to run the generator:

henry@hank:~/swift/libsbp/generator$ python sbp/generator.py -i ../spec/yaml/swiftnav/sbp/ -o ../c/ --c
Traceback (most recent call last):
  File "sbp/generator.py", line 20, in <module>
    import sbp.specs.yaml2 as yaml
ImportError: No module named specs.yaml2

This is after setuptools-installing the latest libsbp and generator packages. It's some path bullshit. I can make it work by copying libsbp/generator/sbp/generator.py into libsbp/generator/, but then I encounter a different error:

henry@hank:~/swift/libsbp/generator$ ./generator.py -i ../spec/yaml/swiftnav/sbp/ -o ../c/ --c
Invalid SBP YAML specification: /home/henry/swift/libsbp/spec/yaml/swiftnav/sbp/bootload.yaml.
Traceback (most recent call last):
  File "./generator.py", line 94, in <module>
    main()
  File "./generator.py", line 71, in main
    file_index = yaml.resolve_deps(*yaml.get_files(input_file))
  File "/home/henry/swift/libsbp/generator/sbp/specs/yaml2.py", line 102, in resolve_deps
    file_index[fname] = read_spec(fname)
  File "/home/henry/swift/libsbp/generator/sbp/specs/yaml2.py", line 63, in read_spec
    raise e
voluptuous.MultipleInvalid: expected a list for dictionary value @ data['definitions'][2]['MSG_NAP_DEVICE_DNA']['fields']

[henryhallam]

cc @mfine

[mfine]

Fwiw, here's what I run into...

# FAIL
$ python sbpg/generator.py -i ../spec/yaml/swiftnav/sbp/ --output_dir ../latex/ --latex 
Traceback (most recent call last):
  File "sbpg/generator.py", line 20, in <module>
    import sbpg.specs.yaml2 as yaml
ImportError: No module named sbpg.specs.yaml2

# OK with a module
$ python -m sbpg.generator -i ../spec/yaml/swiftnav/sbp/ --output_dir ../latex/ --latex

# OK with PYTHONPATH set
$ PYTHONPATH=. python sbpg/generator.py -i ../spec/yaml/swiftnav/sbp/ --output_dir ../latex/ --latex

But this is me and python pathing: