Catch for Invalid .inputrc

Installed phpsh globally (tried locally as well), got the following error:

```
Traceback (most recent call last):
  File "/usr/local/bin/phpsh", line 47, in <module>
    verbose=opts.verbose)
  File "/Library/Python/2.6/site-packages/phpsh/__init__.py", line 477, in __init__
    readline.read_init_file(input_rc_file)
IOError: [Errno -1] Unknown error: -1
```

My .inputrc (from https://github.com/mathiasbynens/dotfiles):

```
# Make Tab autocomplete regardless of filename case
set completion-ignore-case on

# Append a slash when autocompleting symbolic links to directories
set mark-symlinked-directories on

# List all matches in case multiple possible completions are possible
set show-all-if-ambiguous on
```

Added try-catch block and error output when python encounters an invalid inputrc (although not sure what was causing the above inputrc to fire the readline error).