Fix for illformatted rest

[fizyk]

I had illformatted rest documentation. had this lines in my plugin's description:

..code-block::
    [app:main]
    ....
    env = project environment

I was able to upload, but unfortunately I wasn't able to display package's description.
Instead, I get this error (along with long backtrace):

013-03-15 23:33:03,823 INFO  [pyshop.views.base][Dummy-2] dispatch view Show
<string>:35: (WARNING/2) Title underline too short.

[app:main]
....
<string>:35: (SEVERE/4) Unexpected section title.

[app:main]

Here's my fix for this issue.

[fizyk]

hey, I thought a little bit about this, and since cheeseshop is doing the same, we shouldn't try to do anything more here, than display the raw rest in pre tags