Intro to Rust MOOC Section 2

[CrackTheCode016]

Addressing the second module as per https://github.com/w3f/w3f-education/issues/38.

• [x] Variables & Mutability
• [x] Data Types
• [x] Functions & Comments
• [x] Loops

[CrackTheCode016]

I should probably add the following to this section:

• [x] Basic Control Flow (if/else, match)
• [x] Return types, more clarification on expression vs statement

Then it will be ready to merge.