Should ion compile with stable or nightly?

Created by: BafDyce

The current master (6308880f) only compiles with nightly, and also .travis.yml is set up to compile with nightly. However, I think @mmstick once mentioned that ion should target the stable release channel of rustc. This is also supported by the "Compile / Install Instructions" section in the readme. (no instructions to switch to rustc nightly)

So, we (or better: ions core team) should agree on whether ion should always compile with the stable version of rustc or with nightly. Afterwards, the following steps should be done:

• Update .travis.yml
• Add a note about which rustc channel to target to the readme

Things to consider:

• redox requires the nightly toolchain. When compiling redox, the same rustc version is used for compiling ion too (I think). Is it guaranteed for software which compiles with stable rust, to always also compile with nightly? If not, ion should probably target nightly in order to avoid failing builds of redox.