Fixed object indexing by string

Fixed indexing objects by string value:

{
   "a" : .data."hello"
}

Fixed array slicing

Merge pull request #17 from tonysparks/array_slice_fix

Fix array slice syntax issues

Bug fixes!

Bug fixes for:

• multiply string "x" * 3" should equal "xxx"
• object concat should prioritize the left most { "x" : 1 } + { "x" : 2 } should equal { "x" : 1 }
• array slice end index now allows for negative indexing
• for loops now return null if the input is null { if (null) .} should equal null
• proper error handling of binary operations on numbers if they are not numbers (exception with multiplication)
• added replace, trim, substr functions

Async feature

• Introduction of experimental async feature
• Minor bug fixes
• Minor performance optimizations (less generic opcodes)
• More command line options