Missing function setIntegrationTime

[esp13]

Hi,

The function .setIntegrationTime seems to miss in .cpp

I have also noticed some modifications need to be done to use this library:

• We have to adapt some code for ESP32 use : fix compile errors #10 Example build failing on ESP32 and ESP8266 #9
• We have to add missing sleep function : Missing sleep mode to improve power consumption #12
• Anything else to do? Is this library ready to use or better try another? (And witch one? I tried Adafruit's one but there are some dirty delay() inside; and sparkfun one's isn't up to date since last vishay datasheet update)

I also am surprised to get some high UVIndex values (higher than 12) in France (The maximum I get from a September sunny day : 16 . Sensor without any glass or protection). Any Idea why?

Sorry for my low English level

[seancaulfield]

I left out the setIntegrationTime because the UVI calculations will not be accurate, as the forumulae given in the datasheet only work for the default integration time.

I am going to merge the PR #16 as it will allow the setting of the integration time in the begin() function.