[ Release ] NNTrainer 0.3.0 Release

NNTrainer v0.3.0 is released.

**Self evaluation:**
1. Build test:	 [X]Passed [ ]Failed [ ]Skipped
2. Run test:	 [X]Passed [ ]Failed [ ]Skipped

Signed-off-by: jijoong.moon <[email protected]>

nntrainer v0.2.0

Relese nntrainer v0.1.1

Release nntrainer v0.1.0.rc1