Specify GET method when submitting task for CSV load so that worker doesn't return 405

[brenns10]

Hello! I battled with a bit of an issue setting up yelp-love and using the CSV import feature. Apparently the CSV import submits a task to a queue in the worker module, which does the actual import.

The first issue I ran across was that the request for /tasks/employees/load/csv did not seem to get routed to the worker module. I addressed that by uploading the dispatch.yaml file (I used a command found in #5).

The next issue I encountered (which this PR addresses) is that the task would return 405 Method Not Allowed. Turns out that the task function only allows a GET method, but when the task is submitted, the taskqueue.add() function defaults to POST (docs, grep for default to post).

The options were either add POST to the list of allowed methods for load_employees_from_csv, or specify GET in the task submission. In this PR I decided to specify GET in the task submission, since all of the neighboring tasks in views/task.py seemed to be GET only. However, having some methods be GET and some be POST seems like a liability, since there is other code that uses taskqueue.add without specifying the method, and it works fine since those tasks use POST (see logic/love.py and logic/event.py). It may make sense to use POST for all the tasks, if only for the benefit that the next time somebody types taskqueue.add they don't need to know which method type their task uses.

[sjaensch]

@brenns10 Thanks for your contribution!