- Add double precision to LEDC frequency
- Add method for writing frequencies (Tones)
- Add method for writing notes (8 channels polyphony anyone?)

Change is to not be mistaken with SD Card

Add exception decoder and fix layout

Added an Exception handling to the offending urlretrieve() call for the issue #108 https://github.com/espressif/arduino-esp32/issues/108

It's not really a fix but the failure message is much more elegant than the initial stack trace as it hints at the solution to the setup problem rather than confusing the user into Windows problems.

adds autoreset after firmware upload

it's part of esp-idf now and can be used by any project

```make monitor``` has been now added to esp-idf by @projectgus and can be used from any esp-idf project

Tested with (all at the same time):
- MPU9250
- HTU21
- TMP102
- BMP180
- AM2320
- SSD1306

fixes: https://github.com/espressif/arduino-esp32/issues/76
fixes: https://github.com/espressif/arduino-esp32/issues/5
fixes: https://github.com/espressif/arduino-esp32/issues/91

make IPAddress.toString() const method, it doesn't modify anything
within the class.

Implementation for Timers 0-4 (no locks yet)

wait for data to be latched and increase timeout in attempt to fix clock stretch issues
Connected issues:
http://esp32.com/viewtopic.php?f=19&t=632&p=2832#p2801
https://github.com/espressif/arduino-esp32/issues/81
https://github.com/espressif/arduino-esp32/issues/53
https://github.com/espressif/arduino-esp32/issues/11

Add instructions for using as IDF component

Fixes issue where switch will not properly trigger if Arduino is used
in IDF as component.
See
https://github.com/espressif/arduino-esp32/issues/83#issuecomment-265326
071

- Link to Windows instructions
- Update instructions for Linux and Mac

Fix formatting and numbering

fixes: https://github.com/espressif/arduino-esp32/issues/76