Fix (sqrt(12)/sqrt(6))**2 simplification
Add a test for printing

Here is the original bug:
https://github.com/sympy/csympy/issues/204#issuecomment-46774428
Add a test for (sqrt(12)/sqrt(6))**2
Rearrange the imports a bit
Merge pull request #232 from certik/Fix_#204_print_error

Add a test for printing
Merge pull request #230 from certik/pow

Fix (sqrt(12)/sqrt(6))**2 simplification
Don't rewrite (x^a)^b, unless b is Integer

The formula (x^a)^b = x^(a*b) only holds if b is an integer.
Add a comment about the power simplification
Only simplify (x*y)^b = x^b*y^b if 'b' is an int
Add tests for power simplification

These fail in master, but pass in this branch.
avoid printing a `*` when `coef_` equals minus one
Merge pull request #236 from certik/pow

Don't rewrite (x^a)^b, unless b is Integer
Merge pull request #237 from thilinarmtb/Fix_#234_Print_error_in_mul

Fix #234: Remove additional `*` when `coef_` is `-1`
Rename umap_basic_int -> umap_basic_num

Because the mapping is from Basic -> Number, and the number can be any Integer,
Rational or (soon) Complex. Not just Integer.
Rename map_basic_int -> map_basic_num
Added divide by zero check in division for Rational
Added tests for catching exception.

* Added CSYMPY_ERROR
* Added CSYMPY_CHECK_THROW
* Added tests for divide by zero for int and rational
Fixed indendatation in all files.

Due to mismatch editor config, some files which I had commented
earlier had mismatched tabs.
Corrected all those files.
There were some alternate files as well, corrected indentation
in them.
Merge pull request #240 from certik/naming

Rename map_basic_int to map_basic_num
Merge pull request #242 from sushant-hiray/fix-indentation

Fixed indentation in all files.