Fixes #239 (No error thrown when a poorly formatted RegEx is used to create a tag rule)

The changes in this commit attempt to create a regular expression using the value passed
into the POST method used to create new tag matchers whenever the comparison method
passed in is a 'like' comparison method (and catches any errors that might be thrown,
returning a sensible error back to the user).
Merge pull request #240 from tjmcs/tb/catch-regex-tag-add-error

Fixes #239 (No error when a poorly formatted RegEx is used with tag_rule)