Created `Catchment` object.
Setup documentation
Setup documentation
qmed by channel area
Added tests for QMED by area
QMED by area is catchment area!
QMED from 1999 descriptors
Added `AmaxRecord` object and QMED from AMAX
Added convenience method to use best available QMED method
Seperated QMED analyses from catchment. Added 2008 method.
Added urban adjustment factor
Added donor adjustment.
Merge pull request #19 from faph/feature_catchment

Catchment and QmedAnalysis classes