Add some remarks about how to setup Twitter
Provide ISO8601_FORMAT and ISO8601_FORMAT_MICROSECONDS constants
Sanizite sys.path when loading plugins.

In order to avoid local modules shadowing system-wide ones (due to
messing with sys.path in rapport/cli.py).
Add default values
Initial take on e-mail functionality

Currently composing e-mail via xdg-email works.
Add 'report' module

It will collect report-specific code. Some code from rapport.cli
is supposed to be moved here.
Add "show", "list" and "email xdg" CLI commands

The former two are for listing and displaying reports. The latter allows
to compose via xdg-email (and thus open up your preferred mail in
KDE/GNOME/XFCE/etc.).