Toc: Pass errors if no atx headers are processed.

Fixes issue #102
Merge pull request #103 from fmoralesc/patch-1

Toc: Pass errors if no atx headers are processed.
Remove useless line in toc function.
Add unit tests and travis support.
Merge pull request #128 from cirosantilli/unit-test

Add unit tests and travis support.
Fix () [] were rendered as links when not in link.
Merge pull request #122 from cirosantilli/paren

Fix parenthesis () and square brackets [] that were rendered as links when not in link.
Add LateX $ and $$ math support.
Merge pull request #123 from cirosantilli/math

Add LateX $ and $$ math support.
Merge pull request #125 from cirosantilli/remove-useless-line

Remove useless line in Toc funciton.
Support YAML headers
Patch YAML frontmatter pull request.
Merge pull request #124 from cirosantilli/front

Support YAML frontmatter headers v2.
Highlight angle braced hyperlinks.

Also fix autolinks without angle braces which
were not being highlighted on top level.