v1.8.0 to fix `multiple-definitions` linker error and drop `src_cpp` and `src_h` directories

Releases v1.8.0

1. Fix multiple-definitions linker error. Drop src_cpp and src_h directories
2. Add example Argument_Complex_Multi to demonstrate how to avoid multiple-definitions linker error in multiple-file projects

v1.7.0 to fix bug resulting wrong frequency for some low frequencies.

Releases v1.7.0

1. Fix bug resulting wrong frequency for some low frequencies.

v1.6.0 to fix bug resulting half frequency when using high frequencies

Releases v1.6.0

1. Fix bug resulting half frequency when using high frequencies. Check Frequencies are half of what I expect #22
2. Add example to demo High Frequency
3. Delete Blynk-related examples
4. Add changelog.md

Release v1.5.0 to add Timer3 and Timer4 support to ATmega32U4 and ATmega16U4.

Releases v1.5.0

1. Add Timer3 and Timer4 support to ATmega32U4 and ATmega16U4.
2. Add Timer auto-selection to examples.

Release v1.4.0 to add support to Generic or Sparkfun AVR ATmega_32U4, ATMEGA_328P and ATmega128RFA1 boards

Releases v1.4.1

1. Add support to Generic or Sparkfun AVR ATmega_32U4 such as AVR_MAKEYMAKEY, AVR_PROMICRO, etc.
2. Add support to Generic or Sparkfun AVR ATmega_328(P) such as ARDUINO_REDBOT, ARDUINO_AVR_DIGITAL_SANDBOX, etc.
3. Add support to Generic or Sparkfun AVR ATmega128RFA1 such as ATMEGA128RFA1_DEV_BOARD, etc.

Release v1.4.0 to add support to Adafruit AVR ATMEGA_32U4 and ATMEGA_328(P) boards

1. Add support to Adafruit AVR ATMEGA_32U4 such as AVR_FLORA8, AVR_FEATHER32U4, etc.
2. Add support to Adafruit AVR ATMEGA_328(P) such as AVR_FEATHER328P, AVR_METRO, etc.
3. Update examples

Version v1.3.0 to add support to AVR AtMega16U4, AtMega32U4 such as Leonardo, YUN, ESPLORA, etc.

Releases v1.3.0

1. Add support to AVR ATMEGA_16U4, ATMEGA_32U4 such as Leonardo, YUN, ESPLORA, etc.
2. Update examples

Version v1.2.0 to optimize code and add better debug feature

Releases v1.2.0

1. Add better debug feature.
2. Optimize code and examples to reduce RAM usage

Version v1.1.2 to clean-up all compiler warnings possible and optimize examples.

Releases v1.1.2

1. Clean-up all compiler warnings possible.
2. Optimize examples to reduce memory usage by using Flash String whenever possible.
3. Add Table of Contents

Version v1.1.1 to add example and modify Version String

Releases v1.1.1

1. Add example Change_Interval
2. Bump up version to sync with other TimerInterrupt Libraries. Modify Version String.
3. Add new h-only code besides conventional h/cpp code