Reason:
For example, if an url is lack of leading 'http:' by mistake, it causes to http_parser_parse_url() cannot parse http host item,
and then pass the null host pointer to _get_host_header(), crash happens.
Fix:
http added null pointer check now.
Closes https://jira.espressif.com:8443/browse/ESPAT-953
* changing dependencies from unity->cmock
* added component.mk and Makefile.projbuild
* ignore test dir in gen_esp_err_to_name.py
* added some brief introduction of CMock in IDF