ignore man and mass in doc
add document custom css style
add generator given piecewise hazard function

* implement single event/observation generator given
  a piecewise hazard function
fix miss-spelled var, plot relative hazard g
fix typo in filename

* harzard -> hazard
Merge remote-tracking branch 'origin/wush-harzard_gen'

Conflicts:
	.gitignore
	NAMESPACE
remove unused feature. Replaced by nleqslv