update get.py and add get.exe

- get.exe is clickable and will soon download binary form of esptool,
which will really simplify installation on Windows
- get.py does not require any extra modules on Linux and Mac
- ```pip install requests``` required only on Windows (if not using
get.exe)
- Paths are made relative to the file in order to make the windows
executable clickable.

README.md

@@ -33,7 +33,6 @@ Most of the framework is implemented. Most noticable is the missing analogWrite.
   curl -o get-pip.py https://bootstrap.pypa.io/get-pip.py && \
   sudo python get-pip.py && \
   sudo pip install pyserial && \
-  sudo pip install requests && \
   mkdir -p ~/Documents/Arduino/hardware/espressif && \
   cd ~/Documents/Arduino/hardware/espressif && \
   git clone https://github.com/espressif/arduino-esp32.git esp32 && \
@@ -52,7 +51,6 @@ Most of the framework is implemented. Most noticable is the missing analogWrite.
   wget https://bootstrap.pypa.io/get-pip.py && \
   sudo python get-pip.py && \
   sudo pip install pyserial && \
-  sudo pip install requests && \
   mkdir -p ~/Arduino/hardware/espressif && \
   cd ~/Arduino/hardware/espressif && \
   git clone https://github.com/espressif/arduino-esp32.git esp32 && \