V0.3 Merge

[sinlerdev]

This pull request is responsible for merging the V0.3 code to the master branch. While work code wise is finished, there are a few stuff that need to be finished first.

List of todo:

• [x] #19
• [x] #18
• [x] #16
• [x] #15
• [x] #14
• [x] #13
• [x] #9
• [x] absent -- Record recode
• [x] absent -- refine unit testing
• [ ] absent -- strict typing
• [ ] absent -- write docs