Prettifying the plantings page.

Added a couple of tiny methods on Crop, and delegated them across to
Planting, to easily display the default/first scientific name, and to
show the number of times a given crop's been planted.

Sadly, the tests randomly fail on my box saying "No route matches
{:controller=>"plantings", :action=>"show"}" which is just nonsense. I
have no idea why it's doing that, so I'm committing it anyway, in the
hopes that either someone can tell me what's up, or else it's just a
glitch on my dev box.
Minor tweaks to plantings page.

Tests still broken for me.  WTF is this even?
Merge branch 'dev' of https://github.com/Growstuff/growstuff into prettier-plantings
added 'where' to planting info (incl. location if known)
Fix one-argument calls to link_to.

Fixes broken tests.
Don't show () on plantings/show if no location given.

Can someone explain the semantics of nil and defined? to me?
Stringify gardens as their names.
Simplified some code using Garden.to_s.
Test display of location on plantings/show.

As discussed at
https://github.com/pozorvlak/growstuff/commit/d87a1ee4fdd15153537382ddbfa16e3e3d9672a5.

The version of app/views/plantings/show.html.haml from commit 97ce623
fails the "()" test, as expected.
Merge pull request #117 from pozorvlak/prettier-plantings

Prettier plantings