Added threading header
Added threading implementation for uCOS-III
Updated README with threading example.
Rename os_thread_sleep_ms()
Updated package file.
Improved comments.
Improve code readability.
Initialize system timer when running os.
Forgot to include header.
Fixed compiler warning in critical sections.
Merge branch 'master' into ucos-iii-threading-impl

Conflicts:
	package.yml
Added a function to sleep a guaranteed duration.
Updated header file.
Use correct timeout for mutexes.
Added missing include.
Corrected mutex timeout unit to microseconds.
Changed thread sleep unit to microseconds.
Merge pull request #40 from nuft/ucos-iii-mutex-impl

Mutex timeouts in microseconds
Merge pull request #39 from nuft/criticalsection-unused-var-fix

Unused variable warning in critical section
Merge pull request #38 from nuft/ucos-iii-threading-impl

Threading api with uCOS-III implementation