update comment and remove 1.9.3 w/o ec as an allowed failure on travis
fix coverage on crl_number_file and crl_list_file loading from YAML
rename ProfileEnforcer to CertBuilder + add features

* CertBuilder now takes :extensions, which will merge with the profile's
  extensions. Any duplicates will be overridden by the new ones supplied
* A few README fixes
* This fixes #59
Remove :san_names from CertBuilder, add validity check. fixes #46

* CertBuilder#build_and_enforce no longer takes a :san_names param. You
  should now build the SubjectAlternativeName extension and pass it in
  via :extensions.
* CertBuilder#build_and_enforce now takes not_before and not_after as
  optional keys. If provided not_after will be checked to verify that
  it does not exceed the lifetime of the issuing CA and then both
  not_before and not_after will be copied to the return hash. If you do
  not supply these keys they will not be present in the return hash