See #48: Ugly fix for bug in emacs url-http package

Since we are supporting 24.3 now we need to fix that the url-http
package doesn't read the mime-format correctly.

Add support for emacs 24.3, don't auto add to ac-source

emacs 24 doesn't have with-eval-after-load.

At the same time, take the advice from an earlier issue. Don't
autoload into user-controlled variables.

Remove support for older emacs versions

Fix comment and URL syntax highlighting when re-fontifying

sparql-mode.el (sparql-keywords): Stop overriding other faces(, like
the comment face). Add C-j as end-of-comment.

sparql-mode.el (sparql-syntax-propertize-function): Make
syntax-propertize-function skip URLs, but if we see a # we add it as a
beginning of comment.

These changes fixes a bug where the fontification of comments didn't
work properly. If you entered a URL with a #, but didn't close the <>,
the line would be given the comment face until you moved to the end of
the line and force a face update by adding a space or similar. We used
to rely on the fontification to detect if we should add the syntax
property, but it is easier to just ignore the parts that shouldn't be
fontified with comment all together instead.

Merge github.com:ljos/sparql-mode

Make sparql-indent-offset affect indent of blank nodes

Merge branch 'master' of github.com:ljos/sparql-mode

Remove require of async, not needed anymore

Fixes #56

Remove async-package dependency

The async package is more difficult to debug and we don't need it
anymore if we just upgrade the emacs version dependency.

Fixes #48.

Fix mishandling unsucessful request

`results' is a buffer and not a string, need to use
`insert-buffer-substring' to insert the text in the buffer.

Fixes #55