v2.1.0 Release

Merge pull request docsteer#185 from docsteer/2.1_documentation

Documentation Updates

Merge pull request docsteer#174 from docsteer/overall_snapshot_ind

Add overall Snapshot match indicator

Add build badges

Add Travis and Appveyor badges to the README

Attempt fix Travis Linux build; set pre-release

Set pre-release flag; unset shell command not supported in Travis?

Merge pull request docsteer#125 from docsteer/2.0.1

v2.0.1 Release

Merge pull request docsteer#121 from docsteer/per_source_switch_snapshot

Add Snapshot per-source enable/disable functionality

Merge remote-tracking branch 'marcusbirkin/hotfix/docsteer#109' into …

…2.0.1

Typo in WinXP version

Fix trailing space