Add custom category url parameter support

Can now support ".../map/index.html?category=Food" as url
Merge pull request #4 from finetjul/category-url-parameter

Add custom category url parameter support
Add subcategories
Add fade from white to make the loading feel less long
Speed up marker loading by removing useless elements from parsing
Merge pull request #5 from finetjul/add-subcategories

Add subcategories