Change replace method in generateSignature

[BigFax]

replace method doesn't make a replacement when the parameter is a string. It converts it to a Regex without the g flag.
The consequence is that it will just replace the first occurrence found in the string. If signatures have mutliple =, + or \ after convertion, just the first occurrence will be replaced and the signatures comparaison will fail.

To make a real string replacement, we need to do string.split('=').join(''); or to pass directly a Regex with g flag.

This PR will fix #9

[lmammino]

Thank you! Great catch!