Fix "cd" when file or directory not found.
Tilde replacement almost working
Fix issue with trailing whitespace causing commands to treat as arg

- trim whitespace, solving issue of whitespace being considered arg
- parse() now duplicaites `line` and therefore does not manipulate
  original
- using defined preprocessor constants for buffer lengths, etc
Add logging for debugging
Fix logging
Merge branch 'tilde' of github.com:Glavin001/MRShell into readline

Conflicts:
	src/mrsh.c
Merge branch 'tilde' of github.com:Glavin001/MRShell into readline
Finish implementation of ~ alias for $HOME.

See https://github.com/Glavin001/MrShell/issues/16#issuecomment-64123560