Add logic to ignore .txt files unless they match the dictionary key:value pair

[AndrewRathbun]

flat text files without the BOM signature (EF-BB-BF) are going to generate lots of false positives

[AndrewRathbun]

Maybe a case statement in CheckFileSignature to handle .txt files in a special way. Might help with #4 as well

[kacos2000]

Don't forget to include other text file formats with no file signature (eg json, xml, log, etc)