#105: Failing tests due to leading whitespace (indentation).

Added some failing tests that should pass if leading whitespace is
trimmed as expected.
#105: Trim equal amount of leading whitespace from all lines to allow for indenting entire presentation.
#105: Failing test due to blank lines without indentation.
#105: Ignore completely blank lines when detecting minimum whitespace.

Don't treat newline as whitespace; only consider spaces/tabs
Ensure there's at least one (non-newline) character on the line
Plus some gymnastics because extracting captures in JavaScript is ugly
Fix lint error in RegEx helper.
Merge pull request #106 from DanTup/master

Support indented contents in textareas