Version bump to 1.0.1d
BUG: Fix unhelpful key error message when incorrect args passed.

For some commands, passing an invalid command line argument would result
in an unfriendly and confusing KeyError message. This has now been fixed
and a UserFeedback exception is raised instead.
FEATURE: Make it easier to create jinja2 filters.

jinja2 filters let you do things like `{{ foo | indent(4) }}`. A few
functions were exposed as filters but in a very ad-hoc, hard-coded way.
Now a `filters` setting controls which template plugins are exposed as
filters, and plugins can additionally specify that certain of their
elements be excluded (for example, the BeautifulSoup module is exposed
in the bs4 template plugin, but it doesn't make sense for this to be a
jinja2 filter). Existing filters were also cleaned up.
FEATURE: Add assertion template filters.

Added several assertion filters to allow making assertions within jinja
templates.

Additionally, the output of `dexy env` has been modified so that
functions which can be used as jinja filters are marked with an
asterisk.