More checking for terminal capabilities

[thisisparker]

cursewords doesn't need many capabilities to run, but the terminal needs to, e.g., understand UTF-8 encoding and in the future it may become important to know what its color situation is like. This should be checked up front and should provide helpful information about what's missing.

[thisisparker]

Honestly I think this is a moot point, a few years later. Maybe I'll figure out where it hits an error and bail a little more gracefully there, but I'm pretty comfortable assuming UTF-8 support now.