options.prettyPrint can now be a function

If options.prettyPrint is a function, meta will be run through it before appending to output.
Update README.md

Need double-quotes around a string containing single-quotes
Merge pull request #295 from ash211/master

Update README.md
Added license type and reference to LICENSE file to the package.json
[fix] add missing markdown links

7dc2a43 removed a number of links from the README. These are still in
the markdown document so currently do not show correctly
Merge pull request #298 from shapeshed/patch-1

[fix] add missing markdown links
Merge pull request #297 from zubairov/patch-1

Added license type and reference to LICENSE file to the package.json
[doc] Add `Installation` section to the README

Fixes #314.
Merge branch 'master' of github.com:zuk/winston

Conflicts:
	lib/winston/common.js
Merge branch 'master' of github.com:flatiron/winston