Improve tooltips by always showing the docstring of the function being called

[harryscholes]

IPython

Pressing shift + tab when calling a function f displays the docstring of f:

IJulia

The behaviour is different in IJulia. If a number is given as the first argument, then no tooltip is displayed:

However, if a defined variable x is supplied, then the docstring of x is shown:

Shouldn't we make the tooltip always show the docstring of the function being called?

[stevengj]

Improvements to the get_token function (used to decide what to request help on) are welcome:

IJulia.jl/src/handlers.jl

Lines 153 to 160 in 397d190

	function get_token(code, pos)
	# given a string and a cursor position, find substring to request
	# help on by:
	# 1) searching backwards, skipping invalid identifier chars
	# ... search forward for end of identifier
	# 2) search backwards to find the biggest identifier (including .)
	# 3) if nothing found, do return empty string
	# TODO: detect operators?

[rongcuid]

Sent a pull request #847. Please review it some time.