Fix/user testing bugs

[francamps]

A series of bug fixes and styling refinements are included in this PR.

• Sources' overlay spacing issues have been fixed.
• Tags are now called filters, and are set in different tabs as Categories. They both have new icons.
• Movement types are optionally custom styled from config
• Timeline has option for hard limits from config.
• Event dots in map display color slices based on aggregate category events they contain
• Cards display precision level for both time and location.

closes #75

[breezykermo]

A couple of things:

• I haven't set up Travis yet, sorry. Could you run a yarn lint manually and fix any errors?
• Do you think it makes sense to switch all tags in the code to filters? I do feel that filters are a more appropriate monikor for what we have been referring to as tags.
• Let's put a default rangeLimits value in the initial store that is commented out, to indicate that it can be changed through 'config.js'.