zvsh: escape nvram values more consistently

I dug into the ZRT config parser code and believe this should be a
more correct and complete way to escape the values we put into the
nvram files.

Before, a command line argument like '"quoted"' would have been put
into the nvram file as

  args = "quoted"

and this is wrong: the outer quotes are removed by ZRT when is parses
the nvram file. We now correctly escape double-quotes as well as
space, comma, backslash, and newline.
zvsh: expand command about escaping cmdline args
zvsh: fix long line
zvsh: fix a "line too long" pep8 error
Merge pull request #23 from larsbutler/zvsh-pep8

zvsh: fix a "line too long" pep8 error
Merge pull request #22 from mgeisler/escaping

Fix command-line args escaping
added mapping stanza for regular files

When nexe is invoked with regular files as arguments, map these as regular files inside zerovm sandbox too

Ex.
When running:
$ zvsh cat.exe @file.txt

The mapping section in nvram will contain:

[mapping]
channel=/dev/1.file.txt,mode=file
Merge pull request #24 from pkit/add_mapping

added mapping stanza for regular files
.coveragerc: ignore test coverage for zpmlib/tests

The test code in zpmlib/tests should not be included in the collection
of test coverage metrics.
tox: revise test coverage configuration

This change removes the `cover` configuration and adds command-line test
coverage reporting for the py27 and py3 configurations. Without this
revision, test coverage is only run with python2.7.
tox: remove duplicated test collection

Having `zvshlib` specified in two places as an argument of `py.test`
results in duplicate test collection. This change fixes that.
tox: add `full` configuration to default env list
Merge pull request #25 from larsbutler/test-cleanup

Test cleanup
tox: put flags on single lines

This makes it easier to add new flags in the future.
tox: generate XML coverage report
Merge pull request #26 from mgeisler/tox-xml-report

Tox xml report
pep8 formatting changes for zvapp
Merge pull request #28 from pkit/zvapp

pep8 formatting changes for zvapp
altered zvapp usage of configparser

changed the method, according to https://github.com/zerovm/zerocloud/commit/a86a230b4a8739b4208d6eaffa363ceec252aa78
Merge pull request #29 from pkit/zvapp

altered zvapp usage of configparser