CLN: Moved image percentile code into separate function, for profiling
PERF: Allow duplicate maxima filtering to be turned off
TST: Check proper rejection of local maxima near edge.
BUG: Local maxima near edges

The region at the image edges from which local maxima were excluded depended on 'separation'. It now depends on 'radius'.
Additionally, the test revealed it was 1 px bigger than necessary.
REF: Use np.percentile in place of scoreatpercentile.
ENH: Merge nearby peaks by picking most massive neighborhood.
PERF: Use take method instead of fancy indexing.
Merge branch 'percentile-perf' into working

Conflicts:
	trackpy/feature.py