Merge pull request #14 from jwchong93/master

Merged with Bing Xuan code
Implement safe memory dereferencing.
Create Exception module for safe commands.
Merge branch 'master' of https://github.com/bingxuan3133/CInterpreter
Add register attribute assignment, shift and rotate operation in mov function
Add ldm stm load/store multiple registers function
Add safe version of ldm and stm (ldms and stms)
Merge https://github.com/bingxuan3133/CInterpreter