Update ledger-mode's "Quick Installation" docs

* Change quote character to '
* Fix indentation
* Load "ledger-mode" rather than "ldg-new"
delete obsolete ledger.texi. Down with cruft!
Merge pull request #211 from mneilsen/master

Update ledger-mode's "Quick Installation" docs
Fix reference to old pattern negation syntax
Merge pull request #212 from bentglasstube/master

Fix reference to old pattern negation syntax
fix README.md build command

--prefix= should not be passed to cmake directly. If the extra '--'
is removed then the prefix get passed correctly to cmake.
Merge pull request #213 from kain88-de/readme_typo

fix README.md build command