Changes to be committed:
  modified:   lib/decoder.js

Well, provided that initialOffset is the value passed as an argument:
console.log(headerLength + totalBytesConsumed === offset - initialOffset)
// true   --- always

1. getSize now is implemented through hash not switch statement.
   More concise and appear to be much faster.

2. Created helpers.js file, and functions that logically unrelated
   to decoding/encoding will go there.

3. Where possible prefer flat code that nested branches

4. In decodeExt dramatically simplify all the things.

Changes to be committed:
	modified:   lib/decoder.js
	new file:   lib/helpers.js

It's caused by not incrementing offset after reaading first byte.
To handle this change I first of all introduce "initialOffset" and
change everywhere offset to "initial offset". This commit does
this part of the job.

Then I will clean 1-by-1 every affected function and branch.

1. Remove "else" statements that go after "return"
2. Where appropriate (another 1-4 bytes have been read) offset is incremented
3. So that expressions like "initialOffset + 2" --- "... + 5" could be replaced by just "offset"

Changes to be committed:
  modified:   lib/decoder.js

1. function decodeSigned (buf, offset, size)
2. function decodeFloat (buf, offset, size)
3. function decodeExt (buf, offset, type, size, headerSize)

Currently:

| RANGE      |  STATUS             | function name (if exists) or type name  |
|------------|---------------------|-----------------|
| 0x00, 0x7f |  MISSING COMPLETELY | positive fixint
| 0x80, 0x8f |  MISSING COMPLETELY | fixmap
| 0x90, 0x9f |  MISSING COMPLETELY | fixarr
| 0xa0, 0xbf |  MISSING COMPLETELY | fixstr
| 0xc0, 0xc3 |  DONE               | decodeConstants(...)
| 0xc4, 0xc6 |  OLD CODE           | decodeBuffers(...)
| 0xc7, 0xc9 |  WIP NOW            | decodeExt(...)
| 0xca, 0xcb |  DONE               | decodeFloat
| 0xcc, 0xcf |  DONE               | decodeUnsignedInt()
| 0xd0, 0xd3 |  DONE               | decodeSigned()
| 0xd4, 0xd8 |  DONE               | decodeFixExt()
| 0xd9, 0xdb |  OLD CODE           | decodeStr(...)
| 0xdc, 0xdd |  OLD CODE           | decodeArray(...)
| 0xde, 0xdf |  OLD CODE           | decodeMap(...)
| 0xe0, 0xff |  MISSING COMPLETELY | negative fixint

…et, size) used

…der.js