replaced pre_lex/post_lex .bind() with .call() as it is several orders of magnitude faster: see also http://jsperf.com/function-calls-direct-vs-apply-vs-call-vs-bind/18

added 'git' target to makefile to simplify the recurring updating back&forth of main vs. gh-pages

augmented the 'site' build rule to nuke any temp files from a previous nanoc run, as those can only lead to obnoxious nanoc crashes.