Wifi fixes

[mesca]

• https://github.com/OpenBCI/OpenBCI_Python/commit/4c8c7c6ef693d2939245df17731f146e84a5d699: Sometimes, lower_sample_object.accel_data is an empty list and accessing its indices will therefore raise an exception. This commit fixes this.
• https://github.com/OpenBCI/OpenBCI_Python/commit/1bf1c853d8423966e76d835131cd87a9cb21708a: In some cases (for instance, when there is more than one network interface), the local IP address detection does not work as expected. This commit allows a custom binding address to be passed to the constructor.

[andrewjaykeller]

Thanks!