Adding .gitignore file.
Added type sig for main; this removes all ghc warnings.
Delinted initial code.
Recast perform with pattern matching instead of case analysis.
Removing unneeded pattern from stripFront; defining strip in point-free style.
Eliminated stray "tail" application; strip input when checking for exit commands.
Simplified repl termination logic code.
Introduced special functions for dealing with Environment objects, in preparation for demoting "perform" from the IO monad.
Streamlined input handling (with functorial application of strip); simplified exit logic.
No more need for Quit as part of Command data structure.
Demoted perform from IO monad - much cleaner abstraction, resulting in simplification of branching logic in repl.
Merge branch 'initial-style-cleanup'