Prevent pie chart from multiple creation

Due to my implementation another pie chart was generated everytime the
statistic tab is clicked. This is now prevented by checking whether the
div element for the pie chart is empty or not.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Harden link checker against nitpicky servers

Apparently, a lot of server have a white list for accepted user agents.
The default user agent of Typhoeus is not part of that list. Hence, I am
using the libcurl user agent from now on. Also adding more configuration
parameters, for instance not checking the host anymore when it comes to
SSL certificates.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Added retries for requests that timed out

Often time outs happen, but almost always this can be circumvented with
a higher connection timeout. While it might be reasonable to just set a
very high connection timeout I decided to use a retry mechanism.

There will be three tries before the check is abandoned. Each try the
connection timeout will be increased by one minute.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add input group with input and buttons

I have added an input box for searching the link checker results as well
as buttons to either display all results, the working links or just the
broken links.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add Angular.JS to the vendor files

I guess I will continue to provide JavaScript features through
Angular.JS. Hence, I have added it with this commit.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Fix default view on the link checker analysis

It takes way too long to load all the link checker results. That is why
I will start with the broken links and make the others available through
the tool bar.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Re-add statistics class to the tab URL

Another victim of the Vim backup file. Just re-added the class of the
anchor tag.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>