Use django-tables2 to render table of lends

The changes in this commit are the bare necessities for creating an HTML table
from a Django data set. Some of the changes are nice: defining how Django data
sets can be transformed into HTML tables with a file named "tables.py" is
familiar and seemingly elegant. Other changes are not so nice:
TEMPLATE_CONTEXT_PROCESSORS has been added to settings.py, the generated HTML is
kinda ugly, and this seems like a heavyweight solution to a seemingly simple
problem.
Pass request context to django-tables2 from view

The documentation for django-tables2 suggests that you "Add
'django.core.context_processors.request' to TEMPLATE_CONTEXT_PROCESSORS". This
is objectionable because TEMPLATE_CONTEXT_PROCESSORS automatically populates the
context (a dictionary-like object passed to every template) for *every*
template.

This commit avoids that undesireable situation by explicitly adding a context
variable "request" to the "lends.html" template. This procedure can be repeated
for those templates which use django-tables2 tables. Much more targeted and
obvious!