Add functions for finding Deal and Task categories.

New functions added to the HighriseAPI class:
  - public findAllDealCategories()
  - public findAllTaskCategories()
  - protected findAllCategories()

New classes:
  - HighriseCategory
  - HighriseDealCategory
  - HighriseTaskCategory

Example usage:
    $deal_categories = $highrise->findAllDealCategories();
    $example_category = $deal_categories['Example']->getId();

    $deal = new HighriseDeal($highrise);
    $deal->setName('Example Deal');
    $deal->setCategoryId($example_category);
    $deal->save();

A test is included in test/categories.test.php.
Correct typos with Exception calls
Don't use addNote() when calling HighrisePerson::getNotes()

Calling HighrisePerson->addNote() causes the note to be saved back to Highrise. This is 1) just plain wrong, and 2) erroneously throws an access exception when you're trying to (erroneously) update someone else's note.

@brycied00d made this commit here: https://github.com/brycied00d/Highrise-PHP-Api/commit/06ecc6b5305c5a7e589e8b99b55a189d46039f23
Merge pull request #1 from ivannovak/patch-1

Don't use addNote() when calling HighrisePerson::getNotes()
Merge pull request #1 from gouch/master

Add functions for finding Deal and Task categories