all supported rubies have rb_fiber_current. drop config flag.
all supported rubies have rb_class_superclass. drop config.
removed TOGGLE_GC_STATS config as it was no longer used.
RUBY_EVENT_SWITCH is unusable for ruby-prof. remove all references.
support profiling gc runs and object allocations for stock ruby 2.1
test with pride only on ruby 1.9.3
added ruby-prof-check-trace to gemspec
require ruby 1.9.3 for building the gem
correct homepage link