Add .md5 extension between URL's filename and its parameters

[petiepooo]

The function below blindly adds a ".md5" to the end of the URL, assuming it has no parameters:

py-idstools/idstools/scripts/rulecat.py

Lines 256 to 258 in a97393d

	def check_checksum(self, tmp_filename, url):
	try:
	checksum_url = url + ".md5"

However, some URLs require parameters, like an oinkcode. It makes sense for the filename extension to be after the filename, but before the question mark character that signifies the start of the parameters. Eg. if the URL is hxxps://example.com/download/rules.gz?oinkcode=g1ty0ur0wn the URL for the hash would be hxxps://example.com/download/rules.gz.md5?oinkcode=g1ty0ur0wn

If there are no parameters specified in the URL, then the .md5 extension should be appended to the end as it is.

[jasonish]

Great, thanks for the PR. Tested with a Snort registered rule set.