Added delete and filelist examples (#11)

Added delete and list file methods to the example section of the readme

Rename authorise => authorize (#7)

While the spelling is interchangable outside of North America, the B2 API
uses authorize, so we should keep the same spelling here to minimize
confusion.

Fixes #6

Add metadata and optimize list files (#4)

* Support all file metadata and implement fileExists

Add support for the missing metadata from the `getFile()` method:
uploadTimestamp, action and bucketId.

Optimize file list retrieval (`listFiles()`) to avoid fetching information
about _all_ the files to get information about a single one. `listFiles`
now support an optional parameter, `FileName`, which will only retrieve
information about that file if it exists. This speeds up the call to
`getFileIdFromBucketAndFileName`.

* Code style fix

* Add metadata to example response test as well

Merge pull request #3 from cwhite92/analysis-zOMVkW

Applied fixes from StyleCI

Rewind the provided resource before uploading

Allow deleting files by bucket name and file name

Allow deleting files by bucket name and file name

Up the maxFileCount parameter for listing files and add a few TODOs

'Allow specifying the file's content type, fallback to b2/x-auto

Update composer.json