ENH: add re.fullmatch
#### Is your feature request related to a problem?

I want to find only strings that match my full regex expression, not just the first part of it.

For example, if I am searching for the string `'panda'`, and my series contains the strings `'panda'` and `'pandas'`, I only want it to return `'panda'`. Currently, using `str.match('panda')` returns both.

#### Describe the solution you'd like

Add support for `re.fullmatch` (https://docs.python.org/3.4/library/re.html#re.fullmatch) so that it can be called with `str.fullmatch`.

