Adding query filters

### Summary

I'm adding some basic string query filters to the api. This sort of closes #88

#### app.py
- Modified `pages_dict` and `paged_results` to consider querystrings.
- Added `get_query_params` function to parse a querystring into a dict.
- Modified `get_organizations` and `get_projects` to filter Organizations and Projects using querystring paramenters

#### tests.py
- Added `test_organization_query_filter` tests
- Added `test_project_query_filter` tests

I'm still missing `/projects?organization_type=Code+for+All`. But I wanted to post this while I finish that.