Allow users to set the maximum length of array that the pretty-printer
will print out.

Currently, jasmine's pretty printer will iterate over an entire array,
formatting every element recursively. For very large arrays, this can
crash the page, or cause a 'slow script' warning.

This commit exposes a 'MAX_PRETTY_PRINT_ARRAY_LENGTH' option. If an
array larger than this is encountered, recursion will stop and the
array length will be printed instead e.g. "Array[20000000]".

The 'MAX_PRETTY_PRINT_ARRAY_LENGTH' option defaults to 100. This is
length of array will not kill your browser, but will allow you
to see big arrays, if you can stomach the output.