Revert "Adding go.mod"

This reverts commit 9e6335e.

Adding go.mod

Merge pull request #5 from ryanuber/f-empty

Add support for replacing empty fields

Merge pull request #2 from ryanuber/e-nopanic

Remove flat string input

Merge pull request #1 from ryanuber/e-panic

api: panic instead of returning error

Don't try indexing backward in strings if they are 0-length

Updated readme to document new config type

Added travis status to README