Fix customization type for evernote-developer-token

This might fix issue #12.
Merge pull request #14 from i-takuya/master

ignore to set value when gdbm has invalid value.
Fixes for #16

I'm not sure what I changed, or if a previous commit fixed the bug,
but I'm not seeing the gsub/Float errors anymore. In fact, everything
seems to work at the moment. Shocking.