Added pin_edge_event as friend class to ipin. Marked ipin and opin ctors explicit
Comment change.
Created pinexcept.h for pin-related exception types and moved existing exception types into it.
Changed copyright year to 2013
Added bad_mode to enum class edge_event_mode
Work in progress: added initial parts of pin_edge_event class & system tests
Added throw of std::system_error on open failure in open_ipin_for_edge_events
Added destructor to pin_edge_event + system tests, added documentation comments
Added bad_pin_edge_event exception type.
Added checking for overwriting existing edge event notification modes in open_ipin_for_edge_events
Added final newline to file.
Added tests for changing pin edge event mode while in use