make JSON first-character check use JSON whitespace

closes #51
deps: type-is@~1.5.2
deps: supertest@~0.14.0
add jsdoc type for main export

closes #53
docs: fix parametersLimit error code

closes #59
deps: on-finished@~2.1.1
deps: mocha@~2.0.0
deps: should@~4.1.0
deps: qs@2.3.0
1.9.1
deps: qs@2.3.2
1.9.2
Default urlencoded extended option to false