escaping unsupported object while printing

Method PRINT-DATA on not specialized types converts theses types to
strings (using princ-to-string) and uses PRINT-DATA on theses strings.

This allows printing of complex types (like hash-tables, objects, etc)
without a readable string representation to be escape printed.

Useful for debugging.
Add support for printing symbols like strings
adds tests for printing unprintable objects and symbols
Use &#39; instead of &apos; to escape #\'. Fixes #12
Fix test case for escaping.
fix escape unreadable objects test

made escape unreadable objects test potable

renamed unprintable-class to unreadable-class
Merge pull request #9 from zickzackv/escape-unprintables

Escape unprintables
Do not trust the *read-default-float-format*.
Merge pull request #13 from fare/master

Do not trust the *read-default-float-format*.
Merge remote-tracking branch 'refs/remotes/origin/master' into api-v2

Conflicts:
	mustache.lisp
	t/test-api.lisp
	t/test-spec.lisp