added failing tests about non reference
Merge branch 'master' into list-items-undef-ref

* master:
  added back php import for scrutinizer
  added banners to readme
  added code coverage via scrutinizer
  finally have all tests of the orinal markdown parser passing
  added more tests ported from original markdown implementation
  improved inline html handling
  improved link and reference parsing
  consistency for HRs
  better tabulator support for lists
  allow html comments
  do not break paragraph on different block markers by default
  added PHP 5.6 to unit tests
  Update README.md
  added basic description to README
  added command line script
  added some tests and fixed small bugs
fixed link and reference parsing to support more sophisticated cases

e.g. nested brackets like [[hi there [this is a
link]]](http://www.cebe.cc)
Merge pull request #16 from cebe/list-items-undef-ref

added failing tests about non reference