Lendingclub

* Don't add null filters. (fixes investing errors in some cases)

* Remove the BeautifulSoup warning by including a parser

* Attempt to blindly fix issue 21: https://github.com/jgillick/LendingClubAutoInvestor/issues/21

* Fix strut token tag value from recent LendingClub site change (issue 10)

* Prevent returning a portfolio (build_portfolio) if LendingClub tries to sneak in a note with an investment amount greater than max_per_note.

* Better error handling when a SavedFilter cannot be found.