v0.8.0

NiLang v0.8.0

Diff since v0.7.3

Closed issues:

• Detect and optimize/error shared write and read-write (#16)
• Detect pre-existing variables. (#28)

Merged pull requests:

• Update statistics.jl (#32) (@HanLi123)
• polish code (#33) (@GiggleLiu)
• Fixed typo (#39) (@dunefox)
• C arithmetic function (#40) (@GiggleLiu)
• Fix grad (#41) (@GiggleLiu)
• no chain call (#42) (@GiggleLiu)