doc(README): Update link (again)

* chore(license): adds missing MIT license file

For my own workflow, I made an adapter to allow passing default values in gleaned from the branch name, but needed to somehow get those values into this adapter, and I thought this was a good way to achieve this goal.

With these changes, my custom adapter can be like this:
```
process.env.CZ_TYPE = "fix"
module.exports = require("cz-conventional-changelog")
```

Instead of having to copy everything.

cz-conventional-changelog can now have its values (specifically all the defaults and maxLineWidth)
through the config.commitizen key in the package.json file.  The scope now automatically becomes
lowercase (as is required for conventional changelogs) and is prompted on the same line (as it is
always short and doesn't need an additional line). The subject question now indicates the total
number of characters that are allowed based upon the maxLineWidth configuration (or 100 as it is now
by default), the length of the type, and scope. Validation prevents entering more than the allowed
number of characters with feedback of the number of characters entered.  Subject will always have a
lowercase first letter and strip any trailing dots (as is required by the conventional changelog
standard).  'commitizen' and 'semantic-release' have been updated to the most recent versions
(because of current vunderabilites) and the .travisci file has been updated to reflect newer node
versions.

BREAKING CHANGE: Node 10 is LTS so please upgrade to it.