tested Esp32 and i2c pin assignment

Define TSL2561_SDA and TSL2561_SCL (e.g. in platformio.ini build_flags) to use pins other than the defaults for i2c, if the board supports it.
Also added pio environment for ESP32.

return 99999.999 lx instead of 0 lx at saturation

if you use autoGain, then normalizedLuminosity and milliLux, you ended up getting 0 lx on saturation at shortest exposure. Now you get 99999.999 lx. I think that makes more sense.

Fix endless loop at full saturation

Merge pull request #6 from joba-1/issue-5

fix for handling saturated sensor

autoGain() waits longer for measurements

as discussed in arendst/Tasmota#2415

increase waiting time for measurements in autoGain() for the benefit of slower chips.

Improved Wire handling

Removes unnecessary calls to endTransmission() as pointet out in #3 by @Koepel and @reloxx13

Swallow insignificant lux digits

This patch adds a parameter for significant digits to milliLux(). Default is 4 digits.

Fix for small platforms and better autogain

This release fixes examples for platforms where long is only 32bit (like e.g. atmega328).
It also improves autogain in cases of very fast increases of luminosity.

No links to make arduino lib manager happy

If you want to build the examples with PlatformIO pio command, see platformio.ini template in examples directory for guidance.

Patch 2.0.2 - replace Serial.printf from examples

fixed issue #2

Changed constructor

Constructor does not take i2c address anymore.
Now the addess is given later with begin(addr) or searched for with begin().