Chore: Bump version to 0.5.5

Use Fiddle::Pointer instead of Ruby arrays for native calls

Force UTF-8 encoding of history entry strings

Fix NilClass error when stdin is not a terminal

reassign Readline constants

Fixes 139

An update to the terminfo entry for xterm-256color made between
ncurses-6.0+20170128-1 and ncurses-6.0+20170429-1 on Arch highlights a
problem with how terminal capabilities were being read and affects all
users of rb-readline on Arch.

The particular terminfo change was to alter the cr (carriage return)
capability from:

  ^M

to:

  \r

The rb-readline code that parses the capabilities was mistakenly storing
this capability as:

  \\r

causing "\r" to be displayed when entering a line of input into an
rb-readline program.

While I am reasonably confident that this change is sound, I am
concerned that there are other problems around the way terminal
capabilities are parsed because this patch fixes only this specific
case. Unfortunately, the `infocmp` line is a maze of regexes and escape
characters and checking and reworking it requires more time than I have
available just now.

Fixes #138.

Tested-by: Mark Somerville <mark@scottishclimbs.com> [Arch, MRI 2.4.1]
Signed-off-by: Mark Somerville <mark@scottishclimbs.com>

In some cases, such as when running tests under minitest, stdin
can get remapped in such a way that shell-outs to commands like
`stty -a` will report "stdin is not a terminal". This can cause
the elements in @_rl_tty_chars to be nil.

In #prepare_terminal_settings, rl_bind_key is called for function
:rl_restart_output, but if @_rl_tty_chars.t_start is nil,
StringScanner.new(seq) in rl_translate_keyseq will throw:

```
Error: no implicit conversion of nil into String
```

This appears to be the only case in the codebase where an unguarded
call to rl_bind_key exists, so this change ensures that we do not
try and map a nil key to :rl_restart_output.

Signed-off-by: Adam Leff <adam@leff.co>

Use Integer instead of Fixnum.

The normal Ruby arrays seem to cause a memory access violation when
compiled with VC.

Fixnum and Bignum are unified in Ruby-2.4 to Integer.

Using Fixnum prints a warning at every start with ruby-2.4.

Fix already initialized constant warnings

Add partial support for escape sequences parsed from inputrc

In order to remove warnings when using this gem, this commit adds a
couple checks to ensure that the constants aren't already defined when
we try to assign them values. This ensures they are set once and only
once.

Update and rename README.rdoc to README.md

Add installation instructions

rbreadline.rb update to use .write

Changed line 6497 from .puts to .write

defaulting to zero when calling out-of-bounds indices on @vis_lbreaks

These are the original names of the commands in GNU Readline. Adding
these aliases allows existing `.inputrc` files which reference these
commands to work properly.

Makes Option-Delete (what Windows / Linux users would likely call
"Alt-Backspace") work on OS X. Restores parity with GNU Readline.

Fix bug when used with pry-remote(drb environment).

See https://github.com/Mon-Ouie/pry-remote/issues/49 .
When we translate Proc object with drb, proc is wrapped with DRbObject.
In this case defined? proc.call is not delegated to proc self.
But proc.respond_to? :call is delegated to proc self.
So here it is better to check `proc.respond_to? :call`.