* Improve Gist Link Regex
While working with the gist liquid tag, I noticed that valid gist links
were resulting in errors. After looking at `gist_tag.rb`, I noticed
that for a link to be considered valid the gist-id had to be exactly 32
characters which is not always true.
I changed the regex so links with a gist-id of at least one character and
at most 32 characters is considered valid. I decided to continue with
the 32 characters that had previously been used as the upper bound. I
also made a change so links with a github username that starts or ends
with hypens or contains consecutive hypens are considered invalid. The
aforementioned change was based on the validation message from the
create new GitHub account form.
* Change gist_link to gist_links in spec file for Gist tag
e04d84bc4c