Check if the size of the number found is between 13 and 19.
This is the PAN length range for major card schemes.
Merge pull request #1 from zendesk/andreionut/fix_pan_length

Check if the size of the number found is between 13 and 19.
Version 0.1.1
Improve the one-line README.md

Bump the version to 0.2.0

Add ggrossman as a contributor and change e-mail to
ggrossman@zendesk.com since eac@zendesk.com no longer valid.
Add length requirements to README

Add License section
Bump .travis.yml to ruby 2.1.1
Create a class method that returns a proc needed for parameter filtering
ready for bump
v0.2.0
Merge pull request #3 from zendesk/vkmita/API-181

Create a class method that returns a proc needed for parameter filtering
v0.2.1
Only sanitize strings
Merge pull request #4 from zendesk/vkmita/only-sanitize-strings

Only sanitize strings
v0.2.2
Add dependency requirement to luhn_checksum
v0.2.3
Formatting plus micro improvements
Use regex with implicit size validation
Credit card can have minimum of 12 characters
Use non capturing group