Add url_name to instance

We want to allow linking to instances with urls like
http://opentreemap.io/philly rather than http://opentreemap.io/12. I
added a unique url_name property to the Instance model that uses a
RegexValidator to ensure a url-friendly value.

The RegexValidator requires all lowercase letters to avoid
confusion, since URLs are case insensitive.
Add view at the root to facilitate testing

Also adds in a couple of ids on the login/logout links to make the
selenium tests work
Add in selenium test driver

Run uitests with:

```
python manage.py uitest
```

This commit just gets everything set up and moving. Future work includes
support for filtering tests on the command line (similar to manage.py
test).

A 'dev-requirements.txt' file that include requirements for running
selenium has also been added. To run the tests you'll need firefox and
some sort of X server.
Modify instance urls to contain name not id

We want to have instance urls like http://opentreemap.io/philly rather
than http://opentreemap.io/12.
Add support for BooleanField to field templatetag and *field.html templates

Since checkboxes are not normally serialized when they are not checked,
inlineEditForm.js and fieldHelpers.js are handling checkboxes separately
from text inputs and selects, and always send true/false when serializing
Add read-only field to plot detail
Merge pull request #273 from ahinz/topic/selenium

Add in selenium test driver
Merge pull request #275 from maurizi/topic/booleanFields

Topic/boolean fields
Merge branch 'master' into topic/instance-url-name

Conflicts:
	opentreemap/opentreemap/urls.py
Merge branch 'master' of github.com:azavea/OTM2
Return failure for exceptions and failures
Rebuild instance.url_name migration

The easiest way to resolve a migration collision when there are no
overlapping models is to simply rebuild one.
Merge branch 'master' of github.com:azavea/OTM2
Re-add in management urls
Minor css updates
Merge pull request #276 from ahinz/topic/merge-in-admin-prototype

Topic/merge in admin prototype
Fix instance url_name creation migration

This migration failed when the instance table contained more than 1 row.
I fixed it by creating the unique instance after generating the url_name
values.
Produce a minified JS bundle and skip source maps unless --dev is passed
Use minified JS bundle when Django is not in DEBUG mode
Merge pull request #277 from maurizi/topic/minifyJs

Minify js