RFC: Use spaces instead of tabs

This is a Request For Comments, based on @shoghicp's commit `ebd771a9fa3f848bfd7294ac8c38db0a1310adf9`, which has now been rebased off the master branch to keep the lines changed counter sane. Please make sure that any changes affecting CONTRIBUTION, code guidelines and project-wide changes have first been accepted through an RFC process with a simple majority vote.

## Topic of the RFC
The offending commit(accidentally pushed to master by @shoghicp, it was originally meant to be to a separate branch :P) involved changing the coding CONTRIBUTION standard of PocketMine-MP to use spaces for indenting, instead of tabs which was the previous standard. The commit also involved re-factoring the entire code base to use spaces for indentation.

The reason for this change is due to a request to change the indenting structure, as can be seen in the link in the update in the comments.

## How to vote
Since this is our first official RFC, any suggestions on how an RFC should be conducted is greatly appreciated. For now however, votes can either vote with a Yes or No vote, **specified clearly as the FIRST sentence** in their comment. Duplicate votes will not be counted.

Example:
```
Yes. I think this should be...
```
or
```
No. This is not required....
```

The vote will close **28 September 2014, 7 days from the creation of this RFC**.

## Final Total Votes
Counted at 28 September 2014 0932 hours (UTC)

| User | Yes | No |
|------|:---:|:---:|
| @Falkirks | | NO |
| @sekjun9878 | | NO |
| @tnpxxsheepdog | | NO |
| @PEMapModder | | NO |
| @Humerus | YES | |
| @ProjectInfinity | YES | |
| @LukeDarling | YES | |
| @ItsBobberson |  | NO |
| @CheesyFriedBacon | | NO |
| @KnownUnown | | NO |
| @iksaku | | NO |
| @williamtdr | | NO |
| @ijoshuahd | | NO |
| @MegaSamNinja | | NO |
| @Striker209MPE | | NO |
| @zhuowei | | NO |
| @lesander | YES | |
| **TOTAL** | 4 *(24%)* | 13 *(76%)* |

**Total Votes**: 17

## Revisions
Revision 1 by @sekjun9878: 7:19 AM 28 September 2014: Add what the actual topic of this RFC is about and add a total votes counter.
Revision 2 by @sekjun9878 at 1113 22 September 2014 (UTC): @shoghcip has confirmed the reason for the change. The push to master was accidental.
Revision 3 by @sekjun9878 Finish RFC