Updated documentation and added example code

.gitmodules

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+[submodule "wxserver"]
+	path = wxserver
+	url = https://github.com/gshau/wxserver

README.md

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-# SQM_TSL2591
+# Arduino compatible Sky Quality Meter using the TSL2591
+
+This is an application of the TSL 2591 sensor to measuring sky brightness for astronomical applications.  It returns the sky brightness in units of magnitude per square arc-second.  Also accessible to the user are the raw counts of the visible and IR channels.  
+
+Some features:
+ - Adaptive exposure and gain control to reduce noise in low light environment.  
+ - Calibration offset can be adjusted by user with ```setCalibrationOffset```
+ - Noise estimates given assuming signal counts follow a Poisson process
+
+This, along with other Arduino projects, can be placed on an ESP8266 module.  I have written a library for using these modules to push data to an influx time-series database and display these results using Grafana.  Below is a screenshot the Grafana frontend with of one night.  Shown are two sensors, one in a weatherstation taking measurements from the sky, and another in a cabinet to illustrate the noise floor.  
+
+
+![SQM Chart](/screenshots/SQMdual.png?raw=true "SQM Chart")

example/SQM_TSL2591_example.cpp

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+/*
+  SQM_example
+  Uses a TSL2591 sensor as a Sky Quality Meter
+
+  This example code is in the public domain.
+
+  Gabe Shaughnessy
+  Oct 21 2017
+ */
+
+
+#include <Wire.h>
+#include <Adafruit_Sensor.h>
+#include "SQM_TSL2591.h"
+
+SQM_TSL2591 sqm = SQM_TSL2591(2591);
+void readSQM(void);
+
+
+
+void setup() {
+  Serial.begin(9600);
+  pinMode(13, OUTPUT);
+  if (sqm.begin()) {
+
+    Serial.println("Found SQM (TSL) sensor");
+    sqm.config.gain = TSL2591_GAIN_LOW;
+    sqm.config.time = TSL2591_INTEGRATIONTIME_200MS;
+    sqm.configSensor();
+    sqm.showConfig();
+    sqm.setCalibrationOffset(0.0);
+  } else{
+    Serial.println("SQM sensor not found");
+ }
+
+
+}
+
+void loop() {
+  digitalWrite(13, HIGH);   // turn the LED on (HIGH is the voltage level)
+
+  sqm.takeReading();
+  digitalWrite(13, LOW);   // turn the LED on (HIGH is the voltage level)
+
+  Serial.print("full:   "); Serial.println(sqm.full);
+  Serial.print("ir:     "); Serial.println(sqm.ir);
+  Serial.print("vis:    "); Serial.println(sqm.vis);
+  Serial.print("mpsas:  "); Serial.print(sqm.mpsas);
+  Serial.print(" +/- "); Serial.println(sqm.dmpsas);
+
+  Serial.println("======================================");
+
+  delay(5000);
+}

wxserver

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+Subproject commit ac77dc31eac922befc4fdb745548ae9ee77ee600