In Base64 encoding, if result ends in \n, remove it. (Fixes #79, #105)

When the last line of the output of the Base64 "s2r" function has exactly 60 characters, a line break is mistakenly added to the end. This causes issue #79. #105 solves this issue on the decoding side, but the problem is actually here on the encoding die. Now, if the output ends in a line break, we remove it before returning.