Tweak .gitignore pattern

This changes the `.gitignore` patterns to only match the `node_modules`
folder for `node-jscs`, in a way that does not interfere with projects
that check in their `node_modules` folder into git.

Closes gh-575
Add failing test for reading files from stdin

See #564. Files larger than one page size are incorrectly concatenated
when read from stdin.
Properly concatenate large files read from stdin

Array#join, by default, concatenates with a single comma. How useless.

Explicitly specify we'd like to join with the empty string to avoid
introducing syntax errors into JS read from stdin.

Fixes #564
Closes gh-565
CLI: Only read stdin if there were no files supplied and not in tty mode or '-' supplied as first argument. Fixes #563