Ignore invalid sorting types

* When sorting the notes list, passing an invalid sorting type
  would cause Python to raise a KeyError exception. Now the sort
  operation is skipped ifs type is invalid.
Fix tag sorting: File not found error

* When sorting notes by tags, Python would raise a file not found
  error for a path where the save_dir was appended twice.
Fix call to ListPads when sorting by date
Merge pull request #36 from equalsraf/tb-listfixes

Fixes for the notes list
Fixing issue #38.

Support spaces in paths. (changes in handler.py)

Also, reindenting and cleaning up the files, so this commit
is a bit of a mess.
Make explicit the requirement of the conceal feature.

Fixes #40.
OpenPad can take an argument now.

Should acomodate the use-case of issue #39.

A fuller fix could require some mayor changes.
minor tweak of the padlib.pad_local.update function

make it behave well for notes under subfolders.
Update documentation to make requirements explicit.
Implementing solution for issue #39

Adds a prompt that can search or create notes in normal mode
without opening the list.
Add option to skip file renaming

- Added new option g:pad_rename_files to enable disable
  file renaming (default is 1)
- If g:pad_rename_files is set as 0 then
  pad_local.update() will not rename the file
Use first_line as file name for OpenPad

pad#OpenPad() can take a first_line argument to be placed
in the file, however the initial file name is still
set to the timestamp. This commit changes the initial file
name to match the given line

- Replaced timestamp() with a call to PadInfo(...).id in OpenPad
- Removed  (now unused) timestamp import
- Added a docstring to clarify the use of PadInfo with a list of
  strings
Merge pull request #44 from equalsraf/tb-no-renaming

Don't rename files and use first_line as filename for OpenPad