Merge branch 'v1.0.0-beta'

**Package**:

+ All third-party packages are now optional in `setup.py`.

**Interactive Mode**:

+ The user is now informed if `prettytable` module is not installed in
  interactive mode.
+ Added `clrpw` command to remove set password.
+ Added `new` command in help menu.
+ Added `metadata` command.
+ In `status` command, the password is now either `None` or 12
  asterisks.
+ In `new` command, compression and encryption values are now evaluated
  before calling `config.new()` to avoid `AssertionError`.
+ `get` and `remove` commands are now using `shlex.split()`.

**Advanced Mode**:

+ Added LZ4 compression algorithm support.
+ `SUPPORTED` (previously lowercase) and `VERSION` variables are now in
  class scope instead of instance scope.
+ Implemented checksum generation and verification of dictionary.
+ Added `strict` parameter to `load()` method.

**General**:

+ Renamed `aes_support` to `cryptodome_support` in `ciphers.py`.
+ Added `release` variable in `info.py`.
+ Added `full_ver` variable in `info.py`.
+ Code refactor