fix small bug with delete redirect, add caching

1. Fixed a bug with the wrong quotation marks which messed up
   redirect on delete of a file/page.

2. Caching is now implemented, along with 2 new default config
   values, $Use_Caching and $Cache_Extension

The way caching works is through the use of page.md.cache which is just
an already generated html version of the page. It gets saved whenever
a page gets generated, and a page will only get generated when a cache
doesn't exist. When a page is edited, it's cache is deleted which forces
a regen on next page load, providing for efficient caching. This version
will be tagged as v1.1.0 due to the introduction of the new caching
feature.