Corrected sub repos and the following issues fixed:

* #13 - Move update button in membership app to better location: in slm-membership
* #12 - Current page should be highlighted in the navigation
* #11 - Direct new members to the membership page: in slm-frontpage
* #9 - Send better information to GoCardless for the user: in slm-membership
* #8 - Make Join Button work bug: in slm-frontpage