Adding Roadmap / TODO in README.md

* Putting plans into shared artifacts helps people get on the same page
* Also some small formatting fixups
Updates to Troubleshooting section of README

* Going through a certs deployment with @stvstnfrd showed us some
  places where our most common set of assumptions (ubuntu, possibly
  running in a VM) may break Python's mostly-posix expectations.

  This gives people ideas where to look when debugging.
Fix default value for TMP_GEN_DIR
Install via HTTPS in README

By default, installation environments lack Github SSH credentials and
this step fails. Anyone needing to clone via SSH can do so explicitly.

This way, the recommended installation path works out-of-the-box.
Fix Markdown syntax for code literal

The code literal section was missing a closing backtick.
Fix Markdown syntax for ordered lists

Github-flavored Markdown requires an additional indent for code blocks
nested within list items [1].

[1] http://meta.stackexchange.com/questions/3792/how-to-nest-code-within-a-list-using-markdown
Specify sane defaults for demo certificates

Previously, certificate generation expected access to S3.

This shouldn't be required when generating a demo certificate, so we
update the README's sample script to disable S3 uploads.

The sample script now specifies the default demo course_id, instead of a
non-existent course_id.

All command line flags are specified with `--long-options` to make the
options explicit to users, as this is their first exposure to the code.
Update private directory variable
Add note about help options
Merge pull request #21 from stvstnfrd/bug/tmp-gen-dir

Fix default value for TMP_GEN_DIR
Merge pull request #19 from stvstnfrd/readme/install

Update README install steps
README: clarification of LC_ALL use
README: Remove references to specific ops people
Merge pull request #20 from edx/jrbl/README_updates

README: Add Roadmap, update troubleshooting
Fix PEP8: W291 trailing whitespace
Fix PEP8: E128 continuation line under-indented

for visual indent
Fix PEP8: E261 at least two spaces

before inline comment
Fix PEP8: E221 multiple spaces before operator
Fix PEP8: E126 continuation line over-indented

for hanging indent
Fix PEP8: E501 line too long