Updating readability and functionality

Here are my documented changes for each commit, listed by commit, for my branch.

README.md: (6 Commits)
First:
[x] Corrected invalid PHP to valid PHP.
[x] Converted single quotes to double quotes for code cohesion.
[x] Made intro dirextions more detailed.
[x] Rearranged examples to mirror listed methods.
[x] Removed duplicate buy example.

Second:
[x] Updated titles format.
[x] Updated example code format.

Third/forth:
[x] Fixed general display problems.

Fifth:
[x] Updated all code blocks to Github standard, to try and resolve display issues.

Sixth:
[x] Edited 'How to use' title (Removed the question mark)
[x] Updated examples to see current orders (an incorrect/unknown method current_orders() was listed).
[  ] TODO: Find solution to numbered lists resetting after a formatted code bock is inserted into the page.

test.php
Seventh:
[x] Updated the test script.
[x] Converted PHP short tags to standard long tags.
[x] Updated invalid currency pairs.
[x] Added more API tests.
[x] Simplified code output.