Starting with CodeIgniter 3.0, all class filenames (libraries, drivers, controllers and models) must be named in a Ucfirst-like manner or in other words - they must start with a capital letter.
Controllers:
application/controllers/welcome.php
to application/controllers/Welcome.php
Models:
application/models/misc_model.php
to application/models/Misc_model.php
Source: Classes file naming Conversion in CodeIgniter
Note that this DOES NOT affect directories, configuration files, views, helpers, hooks and anything else - it is only applied to classes.
You must now follow just one simple rule - class names in Ucfirst and everything else in lowercase.
and .htaccess
should be
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]
</IfModule>