Adding "dump:manifest" command

```
usage: zinc dump:manifest [-h] -c CATALOG -b BUNDLE -v VERSION [-O]
                          [--no-decompress]

optional arguments:
  -h, --help            show this help message and exit
  -c CATALOG, --catalog CATALOG
                        Catalog reference.
  -b BUNDLE, --bundle BUNDLE
                        Bundle name.
  -v VERSION, --version VERSION
                        Version.
  -O, --remote-name     Write to file using remote name instead of stdout
  --no-decompress       Don't decompress file
```

Example:
```
$ zinc dump:manifest -c games -b pancakes -v latest
```
Would dump the manifest json to stdout
Removing unused requests import
Adding dump:index command and refactoring
Merge branch 'develop' into feature/dump-manifest-command
Merge pull request #24 from mindsnacks/feature/dump-manifest-command

Adding "dump:index" and "dump:manifest" commands