Added new interpreter rules for handling broadcast comparisons and logical operators

[ancorso]

Added rules and tests for handling the following comparisons and operators: .<=, .>=, .==, .&, .|

[coveralls]

Coverage increased (+0.5%) to 87.981% when pulling ae8a37d on ancorso:interpreter_addons into 45158fe on sisl:master.

[rcnlee]

I think this is the best way to implement it at the moment. You can actually call .<=(x,y) like it's a regular function, but unfortunately you can't get a function pointer to it to put into the SymbolTable. Broadcasting like this (<=).(x,y) already works, but isn't as user-friendly as infix. Only infix notation is currently not supported because it parses to an Expr of a different form. I don't see a better to implement infix broadcast at the moment, so I'll go ahead and merge it. If we come across a more general way where we don't have to do individual checks, we can revisit.

Thanks Anthony!