Wording changes

[jwhhh]

• the wordings are inconsistent, change all "solvers" into "tools" (in the two suggest_tools method)
• did you mean 'matrix solvers?' -> did you mean 'matrix solvers'? (move out the question mark)
• remove the line search reference link in cofi.simple_newton
• in cofi.simple_newton, change "max_iterations" into "num_iterations" (make sure all existing examples work)
• shorten error messages (print and raise in some places, instead of raising from)