npm fixes, syntax error, other

I made a few changes:

1) I updated dependencies so that txtool can be used with "npm install" correctly, provided Stephen uploads the changes I just made to libcoin to npm.

2) I edited all dependencies in package.json to specify exactly which version number is required. This ensures that future behavioral changes to dependencies can't break txtool. However, it also means that future security changes to dependencies don't filter down to txtool unless package.json is explicitly updated. It's a trade off.

3) I fixed two syntax errors where there appeared to be an unneeded parenthesis, which I removed.

4) I upped the version number so that these changes can be uploaded to npm.

5) I added "node_modules" to .gitignore.