regression: CLI processing of globs

[dimitropoulos]

The prior version of HTTPSnippet allowed processing of globs on the CLI as follows:

httpsnippet ./*.json --target node --client request --output ./snippets

$ tree snippets/
snippets/
├── endpoint-1.js
├── endpoint-2.js
└── endpoint-3.js

I wasn't aware of this prior functionality (and there were no tests covering it) so it was missed.

Shouldn't be too terrible to add back. Let's have some tests for it this time, too.

Reproduction steps

run the following:

./bin/httpsnippet src/fixtures/requests/*.json --target node --client unirest --output ./example

And it returns this input:

Unknown arguments: src/fixtures/requests/application-json.json, src/fixtures/requests/cookies.json, src/fixtures/requests/custom-method.json, src/fixtures/requests/full.json, src/fixtures/requests/headers.json, src/fixtures/requests/https.json, src/fixtures/requests/jsonObj-multiline.json, src/fixtures/requests/jsonObj-null-value.json, src/fixtures/requests/multipart-data.json, src/fixtures/requests/multipart-file.json, src/fixtures/requests/multipart-form-data.json, src/fixtures/requests/multipart-form-data-no-params.json, src/fixtures/requests/nested.json, src/fixtures/requests/query.json, src/fixtures/requests/short.json, src/fixtures/requests/text-plain.json

When it should, instead, process all of those files.