Fix warning in ratetrace_single()
Fix ratetrace_single() when called directly, not through dplot().
Docs: fix iter_bursts_ph() docstring
Variable renames and style fixes in burstsearchlib.py
Simplify cython burst search gaining ~30% speed.

To recompile the extension go in burstsearchlib folder and type:

    python setup.py build_ext --inplace
Plots: normalize fitted model when pdf=False in hist_burst_data()

Affects also hist_fret() and hist_S()