added no_proxy handler - fixes #1318

- handle no_proxy directive when building stream context
- using CIDR matching from Zend library
- uses parts of code provided courtesy of @hoffman
fix minor typo
return early if rule is * and remove one level of nesting
added documentation for no_proxy env var
Merge remote-tracking branch 'radnan/issue-1318'
Reformat some code and avoid adding proxy auth if no_proxy matched the url, refs #2017
Add tests, refs #2017