Update receive.ino

Fixed /INT handling.
Code would work itself into an infinite loop when on a busy CAN bus.  The /INT line is held low when the receive buffer is full which would prevent the interrupt handler from every setting the flag again.  The code now reads from the MCP2515 whenever the /INT line is in the low state.
Update mcp_can.cpp

Cleaned up mask and filter initialization.
Fixed read_id function bug that causes 0x10000 to be subtracted from an extended ID having a value greater than 0x18000.
The bug stems from shifting the bits over 16 and then adding to it.  Seems to cause undesirable results.
Updated bitrates...

Enabled 3 samples per bit instead of 1 by default.
Fixed some bad baud-rate settings. (I've confirmed 125K and 250K work with a Peak-System PCAN-USB dongle.)
Update README.md
Update README.md
Update receive.ino

Added getCanId() function into example and reformatted the serial output.
Update receive.ino

Oops ;
Updated serial output format

Now prints out something like:
ID: 10EFFFF6  Data: 01 23 34 56 78 90 AB EF
[...]
Removed Division Arithmetic
Confirmed Baudrates
Merge pull request #1 from coryjfowler/master

Made some improvements