HTTP requests now handle errors appropriately. Need to make better documentation
Before Jaime's second merge. Added some methods in the constants file, these are not yet used anywhere
Constructor was missing.
Trying to merge with Jorge's code. This is the result of the upstream merge with his master branch.

Merge remote-tracking branch 'upstream/master'

Conflicts:
	bathsite/data_providers/phylopic.py
	bathsite/treegenerator/views.py