Removed unneded href='#' attributes from popup menus.

Added a css class info-popup for any item that is a popup giving more information
(e.g. the info icon help popups, menus that expand to give more choices, etc.),
which will fix the cursor for links without an href.

Fixes #79.
Load fixtures in auto_link_spec.

Previously, specs would fail in an order-dependent manner based on whether the
fixtures had been loaded by previous specs.

Fixes #80.
Updated persona login javascript.

Fixes #74 as a side effect.
Strains now check for sequences in linked plasmids

only if they don't have one themselves.

Fixes #75.