Added tests to sleep, added nanosleep

[ZetaTwo]

• Added nanosleep (#38)
• Added tests for all sleep variations

> time ./tests/sleep                                                        
./tests/sleep  0,00s user 0,00s system 0% cpu 3,509 total

> time PREENY_DEBUG=1 LD_PRELOAD=./x86_64-linux-gnu/desleep.so ./tests/sleep
+++ Just spared you 1 seconds!
+++ Just spared you 1000000 microseconds!
+++ Just spared you 1 seconds and 500000000 nanoseconds!
PREENY_DEBUG=1 LD_PRELOAD=./x86_64-linux-gnu/desleep.so ./tests/sleep  0,00s user 0,00s system 63% cpu 0,001 total

[zardus]

Thanks!