Replaced tab with spaces, travis file now validates

.travis.yml

 language: cpp
-compiler: 
+compiler:
     - gcc os:
     - linux
     - osx
@@ -14,7 +14,7 @@ notifications:
         recipients:
             - dilawar.s.rajput@gmail.com
             - bhalla@ncbs.res.in
-	    - aviralg@ncbs.res.in
+            - aviralg@ncbs.res.in
             - hrani@ncbs.res.in
             - ray.subhasis@gmail.com
 
@@ -22,14 +22,14 @@ notifications:
         on_failure: always
 
 env:
-    - CTEST_MODEL=Nightly 
+    - CTEST_MODEL=Nightly
 cache: apt
-before_script: 
+before_script:
     - sudo apt-get update -qq
-    - sudo apt-get install libxml2-dev libbz2-dev 
+    - sudo apt-get install libxml2-dev libbz2-dev
     - sudo apt-get install libhdf5-serial-dev
     - sudo apt-get install python-numpy python-setuptools python-networkx
-    - sudo apt-get install make texinfo cmake 
+    - sudo apt-get install make texinfo cmake
     - sudo apt-get install python-suds python-matplotlib
     - sudo apt-get install python-qt4-dev python-qt4-gl python-sip-dev libqt4-dev libopenscenegraph-dev
 
@@ -38,10 +38,10 @@ install:
     - tar -xzvf gsl-1.16.tar.gz
     - cd gsl-1.16 && ./configure --prefix=/usr && make && sudo make install && cd ..
     - wget http://sourceforge.net/projects/sbml/files/libsbml/5.9.0/stable/libSBML-5.9.0-core-src.tar.gz
-    - tar -xzvf libSBML-5.9.0-core-src.tar.gz 
+    - tar -xzvf libSBML-5.9.0-core-src.tar.gz
     - cd libsbml-5.9.0 && ./configure --prefix=/usr --with-zlib --with-bzip2 --with-libxml && make && sudo make install && cd ..
-script: 
+script:
     - mkdir -p _build && cd _build && cmake -DCMAKE_INSTALL_PREFIX=`pwd`/_install -DDEBUG=ON .. && make
 
 after_success:
-    - ctest --output-on-failure 
+    - ctest --output-on-failure