Small improvement for transforming sums of products
Fixed some tests which failed because of syntax changes.

(7 + x) /= (x + 7)...
Fix parser bug

After s, it always expected sin (same for cos, tan)
Rename Euler constant to eu
Simplify's now able to better factor out in fractions

Before:
simplify $ ((y * x * y) / (x * y * y)) --> x * (y)^(2.0) * (x * (y)^(2.0))^(-1.0)
Now:
simplify  $ ((y * x * y) / (x * y * y)) --> 1.0
Some more little changes without huge effect.
Removed superfluous multiplication with 1
enhanced simplifySum's factor-out entry point
Add parsers for Abs and Signum
New exp rule: euler^(ln(x) * y) = x^y

And some tests testing this as well as (x^y)^z = x^(y*z)
Infrastructure for pulling common exponents out of a product
Re-structured chaos at the bottom of Symmath.Simplify (a bit)

It's still a mess...
Restored canceling abilities

re: existential crisis
Six more tests will improve test coverage a lot.
Added some paragraphs to the README

About "Comparison", "Modularization", "Testing".
Better function table, width aligned fields

(thanks to Text.Printf)
Improved product transformation etc
Improved function table functions radically

At this point, a rather good-looking function table can be printed with
this call and looks like the below shown table:

ghci> defaultFunctionTable 0 40 10 (Fraction 1 (Variable 'x'))
              x       (1.0 / x)
--------------- ---------------
         0.0000        Infinity
        10.0000          0.1000
        20.0000          0.0500
        30.0000          0.0333
        40.0000          0.0250

We're also not using any third-party packages anymore for
pretty-printing but the standard Text.PrettyPrint.
Could remove three other rules from simplifyProd
Symmath, Release III.

Merge branches 'pu/simplify', 'pu/parse' and 'pu/funtable' into next