Implement single-level JSON parsing

add function parseSingleLevelJson, that parses JSON object, that doesn't contain nested objects or arrays, to map
Add tests, that check single level JSON parsing function
Fix coding style and typo

add spaces before keywords
rename singleLevelJSON_t to string_pair_t
fix typo in isValidUnquotedCharacter function name
replace == "" by .empty()
Merge pull request #32 from swat32exe/add-single-level-json-parsing

Add single level json parsing