Add method to read from StringIO

[BDunk]

Added a method to allow for a StringIO object to be passed, instead of a filepath.

For probably bad reasons, we have a number of EPW files stored as text in a DB. Cloud deployments can sometimes have a lot of overhead for file read/write.

Separating the file opening from the reading of the file-like object allows us to parse a StringIO object, which can be from a file, or just from our strings.

The API remains backwards compatible, the previous read has been updated to use the stringIO reading function.

All tests are passing (changes dir tests to test because unittest was complaining)

[BDunk]

@rbuffat I know you last wrote to this a decade ago, but it would be really useful for me if you were willing to accept changes and deploy to PyPI?