Fixing typo.

"treees" is assigned and never called, should be "trees".
Subsequently, this assignment is recalculated at a later
stage, removing that.
Fixing whitespace inconsistencies in search function.
Fixing whitespace in tests and improving tests.
Merge pull request #62 from steventlamb/bug/fix_api_tests

Fixing CQL Filtering tests
Refactoring template tags to be more DRY. Adding tag.

The new template tag "unit_or_unknown" is used by one of
the implementation skins.
Merge pull request #63 from steventlamb/topic/refactor_ttags

Refactoring template tags to be more DRY. Adding tag.
Allow "Pests" to be a filterable category
Merge pull request #64 from ahinz/topic/pest-search

Allow "Pests" to be a filterable category