validation for Phone#number length
test phone number validity
Merge pull request #51 from james246/master

validation for Phone#number length
Update README.textile to match the actual API

There is a single `get_invoice` method that either accepts an invoice id
or number and not individual methods as described in the current README.

Fixes #27
Merge pull request #62 from pixeltrix/patch-1

Update README.textile to match the actual API