Fixing a typo in the requests tests;

Added AbortController support;

…cancel-token-leak

…el-token-leak

� Conflicts:
�	package.json

…sending a request;

…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

# Conflicts:
#	index.d.ts
#	lib/adapters/xhr.js

# Conflicts:
#	README.md
#	index.d.ts
#	lib/core/Axios.js
#	test/specs/cancel.spec.js

Updated README;