Use bignumber.js to process numbers over js precision range

This returns them as strings instead of numbers
Adds new dependency on bignumber.js
Optimizes big number discovery, based on code from kai-koch
Adding small information about insert id returning string for big numbers
Moves BigNumber to top of file, fixes bug for first number after ieee754 precision limit
Really fixes checking for big number
Updates parser test
Changes big_number to bigNumber
Add supportBigNumbers to ConnectionConfig (false by default)
Pass config from Protocol to Parser
Change Parser to look for supportBigNumbers option before checking for big numbers
Change Parser to have the previous behavior of throwing when value over number precision (if big number support is off)
Revert Parser test
Changes Readme to mention supportBigNumbers option
Changes RowDataPacket to check for big number support option and don't cast to number if string value is over precision limit
Add one more paragraph about precision limit and supportBigNumbers option
Makes a few changes provided by @kai-koch
More changes... :)
Merge pull request #382 from felixge/bignumber

Changes parseLengthCodedNumber to parse big numbers