Add debugger gem

In order to facilitate future debugging, we are adding the debugger gem
to the project. As this is in the Gemfile generated by Rails, all that
was required to add it was uncomment the line in question and run
bundler.

[#41633207]
Configure application to have UTC as default timezone

This commit sets the default timezone for the app as UTC for both Time
methods and for ActiveRecord. It also removes an unecessary pair of
parentheses attached to a call to `Time.now` which did not match the
style throughout the rest of the project.

[#41633207]
Merge pull request #88 from jcaudle/fix-redirect-spec

#41633207 - Fix redirect spec
Plantings now show up on members and gardens pages
remote "Note" about random selection of crops
Removed 20 random plantings
Showing plantings on crops page. Ugly for now, but works.
Plantings show on members, gardens, and crops pages

Created a thumbnail to standardise the display.  It's not pretty but it
has the basic info.
Small refactoring: use the date format we made
Display thumbnail inside a .well, optionally hide description
Added description field to gardens
Link to the planting, not the crop.

Also, a subheading for the gardens page.
Migration for planting slugs
Slight tweak to garden slug tests
added friendly IDs for plantings, and tests
Merge pull request #90 from gnattery/garden-description

Garden description
Merge pull request #91 from gnattery/friendly-plantings

Friendly plantings
Merge pull request #89 from Skud/planting-links

Planting links
fixed problems with tab display on member profile
Sort crops case-insensitively in the plantings form.