Allows more flexibility downstream

Also some minor documentation and naming changes for consistency.

Set default alphabet for sendSMS

problem was new lines, not time.

Otherwise was going into an endless reading loop because user code only asked for a short part of the total amount of data sent.

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.