Also fixed the "isNetworkConnected" for ESP8266

Also shorted time between checks in "isNetworkConnected" for all modems

- fixed int/uint warning
- added functions to get local IP address with esp8266
- fixed local ip fxn for xbee
- removed extra test builds
- set travis to build all modems in tests

I realized they're not as usable on their own as I expected.

Fixing hex return formats and catching missed wifi/cell differences

I'm remarkably good at getting all of these things to hang..

Added an extra function to empty the buffer between calls and added some extra wait times for responses.