Ask what compilers the user would like us to use?

[robsimmons]

The code that makes the "config" file should probably ask the user for input. Here's the script I'm imagining; I'll do it this weekend if this is agreeable to everyone.

NOTICE: No config file, trying to create /Users/rjsimmon/.smackage/config
NOTICE: To do this, I need to ask you a few questions.
Do you have "mlton" (MLton) installed and on your search path? [Y/n]: Y
Do you have "sml" (SML/NJ) installed and on your search path? [Y/n]: Y
Would you like "mlton" to be the default compiler? [Y/n]: n
MLton and SML/NJ enabled, SML/NJ will be the default compiler.
You can change these settings by editing /Users/rjsimmon/.smackage/config

NOTICE: No config file, trying to create /Users/rjsimmon/.smackage/config
NOTICE: To do this, I need to ask you a few questions.
Do you have "mlton" (MLton) installed and on your search path? [Y/n]: n
Do you have "sml" (SML/NJ) installed and on your search path? [Y/n]: Y
MLton enabled as the default compiler.
You can change these settings by editing /Users/rjsimmon/.smackage/config

NOTICE: No config file, trying to create /Users/rjsimmon/.smackage/config
NOTICE: To do this, I need to ask you a few questions.
Do you have "mlton" (MLton) installed and on your search path? [Y/n]: n
Do you have "sml" (SML/NJ) installed and on your search path? [Y/n]: n
WARNING: No default compiler, smackage will only be able to download code.
You can change these settings by editing /Users/rjsimmon/.smackage/config

[robsimmons]

(This is much less important now given the intended resolution of issue #10)