Add customizable right alignment in list_format

shlex.split() in python2 doesn't work very well with Unicode as
proven already in #66, so we're using ushlex when running on python2.

Specified minimum version of arrow and forced pulling
backports.shutil_get_terminal_size for python versions < 3.3.

User can now mark place in list_format from where he wants to start
right-aligning remaining content. Tab character (\t) is used as marker.

Added also 'top' alias example to topydo.conf which utilizes this
feature and implements #52.

Minor:
    - remove `- 1` from statements setting line width
    - move strip_braces() to topydo.lib.ListFormat and rename it to
      strip_placeholder_braces()

fixup strip_braces

Failure was obscured by other JSON output failures under Cygwin.

This should have caught the bug that was fixed in a92411f7.

Now it conforms to the normal todo.txt CLI output.

Online coverage reports via coveralls.io

"Modules should have short, all-lowercase names. Underscores can be used in
the module name if it improves readability."

Fix unicode values in aliases config in python2

Apparently shlex and ConfigParser.read() don't work well with Unicode
input in python2.

Fix help in prompt mode

`help` is not a real subcommand and without arguments it is of NoneType,
so we need to properly handle it.

This fixes the issue that `ls -F "%p %s"` doesn't work, because the
double quotes weren't interpreted properly.

Reported by @mruwek.

Suppose format string:

 ls_format = %s [%T]

The result would be:

 Test todo item [just now

The final bracket is missing, because it was matched as part of the
placeholder.

This change will only match the closing bracket when the opening bracket
is also present.

This will make sure that %[T] in the format string gets replaced with
the replacing text.

Add %S - truncated version of %s

Properly split alias options wrapped in quotes

If %S is used in list_format, PrettyPrinterFormatFilter will now check
if final result fits on the screen. If not, it will truncate it
accordingly and only then return.

© by @MinchinWeb for `topydo.lib.Utils.get_terminal_size`

%h stands for: "due %D, starts in/started %S"
%H stands for: "%C, %h"

Also reorder %k and %K to maintain consistency in code.

Adjust `PrettyPrinterFormatFilter` to achieve current `topydo ls` output (and more)

Also fix Unicode error for %K when tag contains special characters.

It shows the first todo item to be done, optionally with a filter
applied:

topydo next +Chores @Home

It calculates if actual todo id is shorter than 3 characters and adds
additional space or two to maintain fixed length of this parameter.

Also set %I as default instead of %i to provide compatibility with
tests and.

These conditional characters should be specified **inside** curly braces
({}) and **after** percent sign (%). They can appear in two groups:
before and after particular placeholder.

Example:
"list_format = %{(}p{)}"

If priority of given todo is C, "list_format" set above will now resolve
to (C), but also won't display empty parentheses if there is no priority
set.

Fixes issue mentioned in 8650033b

With interpolation turned on we couldn't properly use '%' in list_format
strings.

So we still have the tags in the master branch.

Thanks to Travis CI and the unit tests, the master branch is almost
always of sufficient quality to be used.

Other pros:

* Wiki content matches the default branch.
* Project stats at Github are up to date.
* Less merge overhead at release time.