need to test mask/toggle
modified enable_interrupts and added toggle/mask
final changes to 4.0.0
ignore interrupted system call
updated installation instructions
updated installation instructions
updated installation instructions in readme
working on new mcp23s17 module
development of mcp23s17 and spi libraries, slightly modified interrupts
finally tidied everything up and moved to v4.0.0
updated spi to have close and open fd methods
moved to v4.0.0
fixed spi del bug