port BEL to new namespace versions

added `bel_upgrade` executable to convert BEL content to new namespaces
based on a change_log.json file (e.g.
http://resource.belframework.org/belframework/20131211/change_log.json)
corrected semver versions
include executable commands; separate api examples
comment separation
travis build
cleanup; standardize directives, remove unused BEL
temporarily remove testing 1.8.7; see #7
added travis build image
Merge branch 'master' into next

Conflicts:
	bel.gemspec
	lib/bel/language.rb
	lib/bel/parse_objects.rb