Symfony 4 compatible

• #235 Making it Symfony 4 compatible, thanks to @TiagoBrito

Make handling of empty strings in CURLOPT_POSTFIELDS consistent

• #206 Make handling of empty strings in CURLOPT_POSTFIELDS consistent

CurlHook now returns integer HTTP status code and fail safe check while opening files on StreamProcessor

• #219 PHP-VCR 1.4 minor cycle
• #192 / #220 CurlHook now returns integer HTTP status codes
• #212 StreamProcessor now checks for file existence when mode is read only

Fixed a bug where the Host header can have its value replaced

• #213 / #215 Don't set Host header in setUrl if already set
• #218 Extra check when Host header was null before

Fixed header being lost and/or replaced and a bug where PUT is turned into POST

• #216 Prevent first header from being lost when combining arrays
• #186 / #187 Always override request method if CURLOPT_CUSTOMREQUEST is set

Curl Options correctly used when POST, better parallel curl requests

• #175 Set POST method when CURLOPT_POSTFIELDS is set
• #151 Fix parallel Curl requests
• #158 / #185 Fix bug with StreamProcessor::stream_lock

Reset request on curl_rest, clones request to avoid segmentation fault on PHP 5.3 and 5.4 with old libraries

#147 Reset request on curl_reset
#170 Removed test for non implemented feature and bumped phpunit
#171 Fixes #153 and #152: SoapClient::__getLastRequest() returns NULL in PHP 5.3 and 5.4

Elaborated library versions support, fixed bug where headers with JSON content couldn't be processed

We are bumping minor instead of patch versions because of small breaks, like symfony event version and the way to handle headers.

#166 Improve versions constraints to better compatibility
#163 Fix for parsing header values that include colons followed by spaces
#164 Documentation and hide old changelogs
#165 Fixed SOAP tests by replacing the public weather API

Support for Symfony 3

Thanks to @dbu for this!
#148 Update composer.json to allow symfony 3

More debug information and silent flag for url_stat

#137 Honor silent flag & prevent error handler catch, thanks to @mdarse
#144 provide more information when not in recording mode, thanks to @dbu