Adding Arb in CMakeList. Arb can be used -DWITH_ARB=yes
Modified Travis to install ARB if WITH_ARB is set

Also updated bin/test_travis.sh
Fix comment message
Update mpfr install command in .travis.yml

The updated command is: sudo apt-get install libmpfr-dev
Added explicit path for gmp
Travis: remove "-v" from tar calls
Remove the --with-gmp
Specify the location of libgmp.so
Installing Arb as an extension of flint

Also removed -v flags to supress output in untar
Arb: specify MPFR library location
Arb: give the GMP paths to "make install"

Thanks to Isuru Fernando (@isuruf) for spotting this.
Merge branch 'arb-fix' into arb

Conflicts:
	.travis.yml
Adding include flags for arb in CMAKE

This is perhaps not the best way, but works for me
@certik will review this once he is back from
vacation
Added `bernoulli` function

* Linked fmpq_t and  mpq_class
* Added tests.
Uodated bernoulli test to check exception if ARB is not present
Upgraded ARB from 2.1.0 to 2.2.0

This should fix issues in travis builds
Updated `bin/test_travis.sh` to link installed libraries for arb
Add build/install flag --define which passes arguments to cmake

python setup.py build --define="CMAKE_BUILD_TYPE:STRING='Debug'; \
WITH_BFD:BOOL=OFF; WITH_CSYMPY_ASSERT:BOOL=ON"

results in

Configuration results
---------------------
C++ compiler: /usr/bin/c++
Build type: Debug
C++ compiler flags: -std=c++0x -Wall -Wextra -fPIC -g -Wno-unused-parameter -ggdb
Installation prefix: /usr/local
WITH_CSYMPY_ASSERT: ON
WITH_CSYMPY_RCP: yes
WITH_CSYMPY_THREAD_SAFE: no
GMP_INCLUDE_DIRS: /usr/include
GMP_LIBRARIES: /usr/lib64/libgmpxx.so;/usr/lib64/libgmp.so
WITH_BFD: OFF
WITH_PYTHON: yes
Python library: /home/ptb/miniconda3/lib/libpython3.4m.so
Python include path: /home/ptb/miniconda3/include/python3.4m
Python install path: /home/ptb/miniconda3/lib/python3.4/site-packages
Cython path: /home/ptb/miniconda3/bin/cython
WITH_ECM: no
WITH_PRIMESIEVE: no
Added `Zeta` class

* Added the basic API
* Added the function definitions
Added tests for zeta, updated test_travis.sh

test_travis.sh now also searches for /usr/local/lib for libarb.so
include flint