…n-primitives

� Conflicts:
�	lib/adapters/xhr.js

…est Content-Type is 'application/json';

Added throwing SyntaxError if JSON parsing failed and responseType is json;
Added transitional option object;
Added options validator to assert transitional options;
Added transitional option `silentJSONParsing= true` for backward compatibility;
Updated README.md;
Updated typings;

Fixed typo;
Added validator.spec.js;

…n-improvements

� Conflicts:
�	lib/defaults.js

… the function context is not specified (for tests compatibility);

…t/json-improvements

…tead of generic ECONNABORTED on request timeouts;

Added support of onloadend handler if available instead of onreadystatechange;
Added xhr timeout test;
Fixed potential bug of xhr adapter with proper handling timeouts&errors (FakeXMLHTTPRequest failed to handle timeouts);

…n-improvements

…t/json-improvements

…n-improvements

� Conflicts:
�	test/specs/transform.spec.js