Watermark

- Fixes string alignment issues when the `-iv`/`--iversion` flag is used.

- The `-iv`/`--iversion` flag now also shows package versions that were imported as `from X import Y`
and `import X.Y as Y`. For example,

python
import scipy as sp
from sklearn import metrics
import numpy.linalg as linalg



%watermark --iversions


will return

(Via contribution by [James Myatt](
https://github.com/jamesmyat)t)

- Shows "not installed" for version of packages/modules that cannot be imported.
- Shows "unknown" for version of packages/modules when version attribute cannot be found.
- Add Python 3.6 and 3.7 to Travis CI builds.
- Add classifiers to setuptools configuration.

Adds a new `-b`/`--gitbranch` parameter that prints the current Git branch.

- Adds a new `-iv`/ `--iversions` parameter that prints the package names and version numbers of all packages that were previously imported in the current Python session. (Via contribution by [Aziz Alto](https://github.com/iamaziz))