Fixing warnings about variable-length arrays in RankTwoTensor.

The w array is not needed.

Refs #1777.
Fixing variable length array warnings in FiniteStrainCrystalPlasticity.

Refs #1777.
Fix warning about comparison between signed and unsigned int

Refs #1777.
std::vector::data() is a C++11 only feature.

http://www.cplusplus.com/reference/vector/vector/data
(Though apparently compilers support it without the -std=c++0x flag.)

@cpritam, I think the .data() code is yours... please avoid using
this, I don't think it's ever really required.
Fixing comparison between signed and unsigned integers.

Refs #1777.
Fixing more uses of std::vector::data().

Refs #1777.
Fixing hidden overloaded virtual function warning.

Refs #1777.

@WilkAndy I believe this is your code? Please take a closer look - you
have overloaded the virtual returnMap() and getJac() functions with
different function signatures.  Is that what you really intended?  If
the functions do something completely different than the base class,
they should be named differently...
Merge pull request #3568 from jwpeterson/fix_warnings

Fix warnings