Upgrade dependencies & fix branch alias to 6.x-dev

• Upgraded to tolerance 0.4 #76
• [dev] Upgraded to silex 2.0 #77
• [dev] Upgraded php-http/mock-client 1.0 #78
• Fixed branch alias to 6.x-dev

Drop symfony/property-access 2.4.X support && enhance ci matrix

See #74

Drop php 5.5 support & justinrainbow/json-schema >=3.0.0 <=6.0.0

See #73

Welcome to atoum 3

Merge pull request #69 from rezzza/accept-atoum-3

Accept atoum 3 as a requirement

JsonPath assertion

Introduction of new steps to use http://jmespath.org to make some more advanced json assertion :

• Then the JSON path expression :pathExpression should be equal to json :expectedJson
• Then the JSON path expression :pathExpression should be equal to:
• Then the JSON path expression :pathExpression should have result
• Then the JSON path expression :pathExpression should not have result

See features to see real use cases

Fixed bad namespace usage of an exception

See #61

Make HTTP & JSON assertion failures print some helpful error context

See #59

Update to Tolerance 0.3.3

This version fixes an annoying bug on stateful waiter

Deal with request failure

• Introduce RestApiBrowser::sendRequestUntil thanks to http://tolerance.io

Replace `egeloen/http-adapter` with http://php-http.org

• BC Break : php requirement is moved to php 5.5
• BC Break : Remove RestApiContext::iSendAPostRequestToWithFormData