Find location of CRF++ binaries from environment variable CRFPP_HOME

Fall back to assumption that CRF++ lives with source
File names can contain +, especially paths to CRF++
Update install instructions
Merge pull request #8 from academia-edu/crfpp_from_env

Find CRF++ binaries from environment variable
Added kudos for David Judd
Merge branch 'master' into convert_for_gem_use

Conflicts:
	bin/parsHed/redo.parsHed.pl
	bin/redo.parsCit.pl
	bin/sectLabel/genericSect/crossValidation.rb
	bin/sectLabel/genericSectExtract.rb
	bin/sectLabel/redo.sectLabel.pl
	doc/index.html
	lib/ParsCit/Config.pm
	lib/ParsCit/Tr2crfpp.pm
	lib/ParsHed/Config.pm
	lib/ParsHed/Tr2crfpp.pm
	lib/ParsHed/Tr2crfpp_token.pm
	lib/SectLabel/AAMatching.pm
	lib/SectLabel/Config.pm
	lib/SectLabel/Tr2crfpp.pm