v0.3.5

Changelog:

• A SoftI2C instance is now required by the constructor.
• The constructor now raises RuntimeError when the sensor is not found on I2C bus.
• The example has been updated to intercept the errors thrown by the constructor.
• The example has been updated to estimate real acquisition frequency with a precision of 1 microsecond.
• The readme has been re-organized to improve readability.