Fix string inconsistency

Only using double quoted strings when needing interpolation.

If git-blame brought you here you may want to read this, the
problem is with git-blame, not this change.

Try running these two lines just once:
```
git config --global alias.praise 'log -p -M --follow --stat --'
git config --global alias.praise-line 'log -p -M --pretty=format:"%h (%an %ai)"  -L'
```

Now in future you can use

`git praise <path/to/your/file>`

or if you want to see the evolution of a specific line or range of lines

`git praise-line <start-line>:<end-line>:<path/to/your/file>`

Some examples you should try:
```
git praise lib/awesome_print/version.rb
git praise-line 8:8:lib/awesome_print/version.rb
```

Inspiration for these aliases:

http://blog.andrewray.me/a-better-git-blame/

init.rb

@@ -1 +1 @@
-require File.join(File.dirname(__FILE__), "lib", "awesome_print")
+require File.join(File.dirname(__FILE__), 'lib', 'awesome_print')